{ "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-2026-34786", "tracking": { "current_release_date": "2026-04-03T15:37:51.316247Z", "generator": { "date": "2026-02-17T15:00:00Z", "engine": { "name": "V.E.L.M.A", "version": "1.7" } }, "id": "CVE-2026-34786", "initial_release_date": "2026-04-02T17:28:42.124558Z", "revision_history": [ { "date": "2026-04-02T17:28:42.124558Z", "number": "1", "summary": "CVE created.| Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (1).| CWES updated (1)." }, { "date": "2026-04-02T17:28:43.691040Z", "number": "2", "summary": "NCSC Score created." }, { "date": "2026-04-02T17:39:42.570883Z", "number": "3", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products connected (3).| References created (1).| CWES updated (1)." }, { "date": "2026-04-02T17:39:44.914521Z", "number": "4", "summary": "NCSC Score updated." }, { "date": "2026-04-02T20:12:01.861459Z", "number": "5", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (3).| CWES updated (1)." }, { "date": "2026-04-02T20:12:12.450083Z", "number": "6", "summary": "NCSC Score updated." }, { "date": "2026-04-03T00:44:15.114507Z", "number": "7", "summary": "Source created.| CVE status created. (valid)| Products connected (2)." }, { "date": "2026-04-03T00:44:18.158899Z", "number": "8", "summary": "NCSC Score updated." }, { "date": "2026-04-03T06:45:58.829075Z", "number": "9", "summary": "Description created for source." }, { "date": "2026-04-03T15:30:58.783648Z", "number": "10", "summary": "Source connected.| CVE status created. (valid)| EPSS created." }, { "date": "2026-04-03T15:31:02.276883Z", "number": "11", "summary": "NCSC Score updated." } ], "status": "interim", "version": "11" } }, "product_tree": { "branches": [ { "branches": [ { "branches": [ { "category": "product_version_range", "name": "vers:unknown/<2.2.23", "product": { "name": "vers:unknown/<2.2.23", "product_id": "CSAFPID-5985093" } }, { "category": "product_version_range", "name": "vers:unknown/>=3.0.0.beta1|<3.1.21", "product": { "name": "vers:unknown/>=3.0.0.beta1|<3.1.21", "product_id": "CSAFPID-5985094" } }, { "category": "product_version_range", "name": "vers:unknown/>=3.2.0|<3.2.6", "product": { "name": "vers:unknown/>=3.2.0|<3.2.6", "product_id": "CSAFPID-5985095" } } ], "category": "product_name", "name": "rack" } ], "category": "vendor", "name": "rack" }, { "branches": [ { "branches": [ { "branches": [ { "category": "product_version_range", "name": "vers:deb/unknown", "product": { "name": "vers:deb/unknown", "product_id": "CSAFPID-2065710" } } ], "category": "product_name", "name": "ruby-rack" } ], "category": "product_family", "name": "bookworm" }, { "branches": [ { "branches": [ { "category": "product_version_range", "name": "vers:deb/unknown", "product": { "name": "vers:deb/unknown", "product_id": "CSAFPID-2065711" } } ], "category": "product_name", "name": "ruby-rack" } ], "category": "product_family", "name": "bullseye" } ], "category": "vendor", "name": "Debian" } ] }, "vulnerabilities": [ { "cve": "CVE-2026-34786", "cwe": { "id": "CWE-180", "name": "Incorrect Behavior Order: Validate Before Canonicalize" }, "notes": [ { "category": "description", "text": "Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Static#applicable_rules evaluates several header_rules types against the raw URL-encoded PATH_INFO, while the underlying file-serving path is decoded before the file is served. As a result, a request for a URL-encoded variant of a static path can serve the same file without the headers that header_rules were intended to apply. In deployments that rely on Rack::Static to attach security-relevant response headers to static content, this can allow an attacker to bypass those headers by requesting an encoded form of the path. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.", "title": "nvd - https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-34786" }, { "category": "description", "text": "Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Static#applicable_rules evaluates several header_rules types against the raw URL-encoded PATH_INFO, while the underlying file-serving path is decoded before the file is served. As a result, a request for a URL-encoded variant of a static path can serve the same file without the headers that header_rules were intended to apply. In deployments that rely on Rack::Static to attach security-relevant response headers to static content, this can allow an attacker to bypass those headers by requesting an encoded form of the path. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.", "title": "cveprojectv5 - https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/34xxx/CVE-2026-34786.json" }, { "category": "description", "text": "## Summary\n\n`Rack::Static#applicable_rules` evaluates several `header_rules` types against the raw URL-encoded `PATH_INFO`, while the underlying file-serving path is decoded before the file is served. As a result, a request for a URL-encoded variant of a static path can serve the same file without the headers that `header_rules` were intended to apply.\n\nIn deployments that rely on `Rack::Static` to attach security-relevant response headers to static content, this can allow an attacker to bypass those headers by requesting an encoded form of the path.\n\n## Details\n\n`Rack::Static#applicable_rules` matches rule types such as `:fonts`, `Array`, and `Regexp` directly against the incoming `PATH_INFO`. For example:\n\n```ruby\nwhen :fonts\n /\\.(?:ttf|otf|eot|woff2|woff|svg)\\z/.match?(path)\nwhen Array\n /\\.(#{rule.join('|')})\\z/.match?(path)\nwhen Regexp\n rule.match?(path)\n```\n\nThese checks operate on the raw request path. If the request contains encoded characters such as `%2E` in place of `.`, the rule may fail to match even though the file path is later decoded and served successfully by the static file server.\n\nFor example, both of the following requests may resolve to the same file on disk:\n\n```text\n/fonts/test.woff\n/fonts/test%2Ewoff\n```\n\nbut only the unencoded form may receive the headers configured through `header_rules`.\n\nThis creates a canonicalization mismatch between the path used for header policy decisions and the path ultimately used for file serving.\n\n## Impact\n\nApplications that rely on `Rack::Static` `header_rules` to apply security-relevant headers to static files may be affected.\n\nIn affected deployments, an attacker can request an encoded variant of a static file path and receive the same file without the intended headers. Depending on how `header_rules` are used, this may bypass protections such as clickjacking defenses, content restrictions, or other response policies applied to static content.\n\nThe practical impact depends on the configured rules and the types of files being served. If `header_rules` are only used for non-security purposes such as caching, the issue may have limited security significance.\n\n## Mitigation\n\n* Update to a patched version of Rack that applies `header_rules` to a decoded path consistently with static file resolution.\n* Do not rely solely on `Rack::Static` `header_rules` for security-critical headers where encoded path variants may reach the application.\n* Prefer setting security headers at the reverse proxy or web server layer so they apply consistently to both encoded and unencoded path forms.\n* Normalize or reject encoded path variants for static content at the edge, where feasible.", "title": "github - https://api.github.com/advisories/GHSA-q4qf-9j86-f5mh" }, { "category": "description", "text": "Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Static#applicable_rules evaluates several header_rules types against the raw URL-encoded PATH_INFO, while the underlying file-serving path is decoded before the file is served. As a result, a request for a URL-encoded variant of a static path can serve the same file without the headers that header_rules were intended to apply. In deployments that rely on Rack::Static to attach security-relevant response headers to static content, this can allow an attacker to bypass those headers by requesting an encoded form of the path. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.", "title": "debian - https://security-tracker.debian.org/tracker/CVE-2026-34786" }, { "category": "other", "text": "0.00029", "title": "EPSS" }, { "category": "other", "text": "4.2", "title": "NCSC Score" }, { "category": "other", "text": "The value of the most recent EPSS score, Is related to (a version of) an uncommon product", "title": "NCSC Score top decreasing factors" } ], "product_status": { "known_affected": [ "CSAFPID-5985093", "CSAFPID-5985094", "CSAFPID-5985095", "CSAFPID-2065710", "CSAFPID-2065711" ] }, "references": [ { "category": "external", "summary": "Source - nvd", "url": "https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-34786" }, { "category": "external", "summary": "Source - cveprojectv5", "url": "https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/34xxx/CVE-2026-34786.json" }, { "category": "external", "summary": "Source - github", "url": "https://api.github.com/advisories/GHSA-q4qf-9j86-f5mh" }, { "category": "external", "summary": "Source - debian", "url": "https://security-tracker.debian.org/tracker/CVE-2026-34786" }, { "category": "external", "summary": "Source - first", "url": "https://api.first.org/data/v1/epss?limit=10000&offset=0" }, { "category": "external", "summary": "Reference - cveprojectv5; github; nvd", "url": "https://github.com/rack/rack/security/advisories/GHSA-q4qf-9j86-f5mh" }, { "category": "external", "summary": "Reference - github", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-34786" }, { "category": "external", "summary": "Reference - github", "url": "https://github.com/advisories/GHSA-q4qf-9j86-f5mh" } ], "scores": [ { "cvss_v3": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N", "baseScore": 5.3, "baseSeverity": "MEDIUM" }, "products": [ "CSAFPID-2065710", "CSAFPID-2065711", "CSAFPID-5985093", "CSAFPID-5985094", "CSAFPID-5985095" ] } ], "title": "CVE-2026-34786" } ] }