{"id":"CVE-2026-34827","summary":"Rack: Algorithmic-Complexity DoS in Rack::Multipart::Parser","details":"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.","aliases":["GHSA-v6x5-cg8r-vv6x"],"modified":"2026-04-06T00:44:18.906605415Z","published":"2026-04-02T17:07:48.279Z","related":["CGA-p338-c56f-p3qc"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34827.json","cna_assigner":"GitHub_M","cwe_ids":["CWE-400","CWE-407","CWE-770"]},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34827.json"},{"type":"ADVISORY","url":"https://github.com/rack/rack/security/advisories/GHSA-v6x5-cg8r-vv6x"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-34827"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/rack/rack","events":[{"introduced":"572a42a705b423ce98ef4e81435d4f60fb0ae53d"},{"fixed":"ae8431120e66e92d1885ab8ec0a553d9cad5ec13"}],"database_specific":{"versions":[{"introduced":"3.0.0.beta1"},{"fixed":"3.1.21"}]}},{"type":"GIT","repo":"https://github.com/rack/rack","events":[{"introduced":"b68251c03788ff39d4a4b25424df7360426e4afd"},{"fixed":"e1f22fdbe99afd2126b6fbf05bb12399359574b7"}],"database_specific":{"versions":[{"introduced":"3.2.0"},{"fixed":"3.2.6"}]}}],"versions":["3.0.0","3.0.0.beta1","3.0.0.rc1","v3.0.1","v3.0.10","v3.0.12","v3.0.13","v3.0.14","v3.0.15","v3.0.16","v3.0.17","v3.0.18","v3.0.2","v3.0.3","v3.0.4","v3.0.4.1","v3.0.4.2","v3.0.5","v3.0.6","v3.0.6.1","v3.0.7","v3.0.8","v3.0.9","v3.0.9.1","v3.1.0","v3.1.1","v3.1.10","v3.1.11","v3.1.12","v3.1.13","v3.1.14","v3.1.15","v3.1.16","v3.1.17","v3.1.18","v3.1.19","v3.1.2","v3.1.20","v3.1.3","v3.1.4","v3.1.5","v3.1.6","v3.1.7","v3.1.8","v3.1.9","v3.2.0","v3.2.1","v3.2.2","v3.2.3","v3.2.4","v3.2.5","v3.2.6"],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-34827.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}