{"id":"CVE-2025-61771","summary":"Rack's multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion)","details":"Rack is a modular Ruby web server interface. In versions prior to 2.2.19, 3.1.17, and 3.2.2, ``Rack::Multipart::Parser` stores non-file form fields (parts without a `filename`) entirely in memory as Ruby `String` objects. A single large text field in a multipart/form-data request (hundreds of megabytes or more) can consume equivalent process memory, potentially leading to out-of-memory (OOM) conditions and denial of service (DoS). Attackers can send large non-file fields to trigger excessive memory usage. Impact scales with request size and concurrency, potentially leading to worker crashes or severe garbage-collection overhead. All Rack applications processing multipart form submissions are affected. Versions 2.2.19, 3.1.17, and 3.2.2 enforce a reasonable size cap for non-file fields (e.g., 2 MiB). Workarounds include restricting maximum request body size at the web-server or proxy layer (e.g., Nginx `client_max_body_size`) and validating and rejecting unusually large form fields at the application level.","aliases":["GHSA-w9pc-fmgc-vxvw"],"modified":"2026-05-18T05:58:13.578173453Z","published":"2025-10-07T14:42:53.366Z","related":["ALSA-2025:19719","ALSA-2025:20962","ALSA-2025:21036","CGA-8xx9-gpxg-qr2x","openSUSE-SU-2025:15621-1","openSUSE-SU-2026:10286-1"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/61xxx/CVE-2025-61771.json","cwe_ids":["CWE-400"],"cna_assigner":"GitHub_M"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/61xxx/CVE-2025-61771.json"},{"type":"ADVISORY","url":"https://github.com/rack/rack/security/advisories/GHSA-w9pc-fmgc-vxvw"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-61771"},{"type":"FIX","url":"https://github.com/rack/rack/commit/589127f4ac8b5cf11cf88fb0cd116ffed4d2181e"},{"type":"FIX","url":"https://github.com/rack/rack/commit/d869fed663b113b95a74ad53e1b5cae6ab31f29e"},{"type":"FIX","url":"https://github.com/rack/rack/commit/e08f78c656c9394d6737c022bde087e0f33336fd"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/rack/rack","events":[{"introduced":"b68251c03788ff39d4a4b25424df7360426e4afd"},{"fixed":"bce149b11154e851c437b5ece1c026c943f4b571"}]}],"versions":["v3.2.1","v3.2.0"],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2025-61771.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"}]}