{ "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-2026-34827", "tracking": { "current_release_date": "2026-04-03T15:38:24.717554Z", "generator": { "date": "2026-02-17T15:00:00Z", "engine": { "name": "V.E.L.M.A", "version": "1.7" } }, "id": "CVE-2026-34827", "initial_release_date": "2026-04-02T17:39:30.379807Z", "revision_history": [ { "date": "2026-04-02T17:39:30.379807Z", "number": "1", "summary": "CVE created.| Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products connected (2).| References created (1).| CWES updated (1)." }, { "date": "2026-04-02T17:39:32.557576Z", "number": "2", "summary": "NCSC Score created." }, { "date": "2026-04-02T18:27:24.173629Z", "number": "3", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (1).| CWES updated (1)." }, { "date": "2026-04-02T18:27:26.428400Z", "number": "4", "summary": "NCSC Score updated." }, { "date": "2026-04-02T20:52:59.102108Z", "number": "5", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (3).| CWES updated (1)." }, { "date": "2026-04-02T20:53:02.103467Z", "number": "6", "summary": "NCSC Score updated." }, { "date": "2026-04-03T00:44:13.331832Z", "number": "7", "summary": "Source created.| CVE status created. (valid)| Products connected (2)." }, { "date": "2026-04-03T00:44:16.705828Z", "number": "8", "summary": "NCSC Score updated." }, { "date": "2026-04-03T06:45:57.696647Z", "number": "9", "summary": "Description created for source." }, { "date": "2026-04-03T15:30:49.134652Z", "number": "10", "summary": "Source connected.| CVE status created. (valid)| EPSS created." }, { "date": "2026-04-03T15:30:52.548329Z", "number": "11", "summary": "NCSC Score updated." } ], "status": "interim", "version": "11" } }, "product_tree": { "branches": [ { "branches": [ { "branches": [ { "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-2026-34827", "cwe": { "id": "CWE-407", "name": "Inefficient Algorithmic Complexity" }, "notes": [ { "category": "description", "text": "Rack is a modular Ruby web server interface. From versions 3.0.0.beta1 to before 3.1.21, and 3.2.0 to before 3.2.6, Rack::Multipart::Parser#handle_mime_head parses quoted multipart parameters such as Content-Disposition: form-data; name=\"...\" using repeated String#index searches combined with String#slice! prefix deletion. For escape-heavy quoted values, this causes super-linear processing. An unauthenticated attacker can send a crafted multipart/form-data request containing many parts with long backslash-escaped parameter values to trigger excessive CPU usage during multipart parsing. This results in a denial of service condition in Rack applications that accept multipart form data. This issue has been patched in versions 3.1.21 and 3.2.6.", "title": "cveprojectv5 - https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/34xxx/CVE-2026-34827.json" }, { "category": "description", "text": "Rack is a modular Ruby web server interface. From versions 3.0.0.beta1 to before 3.1.21, and 3.2.0 to before 3.2.6, Rack::Multipart::Parser#handle_mime_head parses quoted multipart parameters such as Content-Disposition: form-data; name=\"...\" using repeated String#index searches combined with String#slice! prefix deletion. For escape-heavy quoted values, this causes super-linear processing. An unauthenticated attacker can send a crafted multipart/form-data request containing many parts with long backslash-escaped parameter values to trigger excessive CPU usage during multipart parsing. This results in a denial of service condition in Rack applications that accept multipart form data. This issue has been patched in versions 3.1.21 and 3.2.6.", "title": "nvd - https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-34827" }, { "category": "description", "text": "## Summary\n\n`Rack::Multipart::Parser#handle_mime_head` parses quoted multipart parameters such as `Content-Disposition: form-data; name=\"...\"` using repeated `String#index` searches combined with `String#slice!` prefix deletion. For escape-heavy quoted values, this causes super-linear processing.\n\nAn unauthenticated attacker can send a crafted `multipart/form-data` request containing many parts with long backslash-escaped parameter values to trigger excessive CPU usage during multipart parsing.\n\nThis results in a denial of service condition in Rack applications that accept multipart form data.\n\n## Details\n\n`Rack::Multipart::Parser#handle_mime_head` parses quoted parameter values by repeatedly:\n\n1. Searching for the next quote or backslash,\n2. Copying the preceding substring into a new buffer, and\n3. Removing the processed prefix from the original string with `slice!`.\n\nAn attacker can exploit this by sending a multipart request with many parts whose `name` parameters contain long escape-heavy values such as:\n\n```text\nname=\"a\\\\a\\\\a\\\\a\\\\a\\\\...\"\n```\n\nUnder default Rack limits, a request can contain up to 4095 parts. If many of those parts use long quoted values with dense escape characters, the parser performs disproportionately expensive CPU work while remaining within normal request size and part-count limits.\n\n## Impact\n\nAny Rack application that accepts `multipart/form-data` requests may be affected, including file upload endpoints and standard HTML form handlers.\n\nAn unauthenticated attacker can send crafted multipart requests that consume excessive CPU time during request parsing. Repeated requests can tie up application workers, reduce throughput, and degrade or deny service availability.\n\n## Mitigation\n\n* Update to a patched version of Rack that parses quoted multipart parameters without repeated rescanning and destructive prefix deletion.\n* Apply request throttling or rate limiting to multipart upload endpoints.\n* Where operationally feasible, restrict or isolate multipart parsing on untrusted high-volume endpoints.", "title": "github - https://api.github.com/advisories/GHSA-v6x5-cg8r-vv6x" }, { "category": "description", "text": "Rack is a modular Ruby web server interface. From versions 3.0.0.beta1 to before 3.1.21, and 3.2.0 to before 3.2.6, Rack::Multipart::Parser#handle_mime_head parses quoted multipart parameters such as Content-Disposition: form-data; name=\"...\" using repeated String#index searches combined with String#slice! prefix deletion. For escape-heavy quoted values, this causes super-linear processing. An unauthenticated attacker can send a crafted multipart/form-data request containing many parts with long backslash-escaped parameter values to trigger excessive CPU usage during multipart parsing. This results in a denial of service condition in Rack applications that accept multipart form data. This issue has been patched in versions 3.1.21 and 3.2.6.", "title": "debian - https://security-tracker.debian.org/tracker/CVE-2026-34827" }, { "category": "other", "text": "0.00041", "title": "EPSS" }, { "category": "other", "text": "3.9", "title": "NCSC Score" }, { "category": "other", "text": "Is related to (a version of) an uncommon product", "title": "NCSC Score top decreasing factors" } ], "product_status": { "known_affected": [ "CSAFPID-5985094", "CSAFPID-5985095", "CSAFPID-2065710", "CSAFPID-2065711" ] }, "references": [ { "category": "external", "summary": "Source - cveprojectv5", "url": "https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/34xxx/CVE-2026-34827.json" }, { "category": "external", "summary": "Source - nvd", "url": "https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-34827" }, { "category": "external", "summary": "Source - github", "url": "https://api.github.com/advisories/GHSA-v6x5-cg8r-vv6x" }, { "category": "external", "summary": "Source - debian", "url": "https://security-tracker.debian.org/tracker/CVE-2026-34827" }, { "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-v6x5-cg8r-vv6x" }, { "category": "external", "summary": "Reference - github", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-34827" }, { "category": "external", "summary": "Reference - github", "url": "https://github.com/advisories/GHSA-v6x5-cg8r-vv6x" } ], "scores": [ { "cvss_v3": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH" }, "products": [ "CSAFPID-2065710", "CSAFPID-2065711", "CSAFPID-5985094", "CSAFPID-5985095" ] } ], "title": "CVE-2026-34827" } ] }