{"id":"CVE-2025-61770","url":"https://www.cyber-defence.io/tools/cve/CVE-2025-61770","generatedAt":"2026-10-28T09:41:51.760Z","title":"Remote attackers can trigger large transient memory spikes by including a long preamble in multipart/form-data requests.","description":"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` buffers the entire multipart preamble (bytes before the first boundary) in memory without any size limit. A client can send a large preamble followed by a valid boundary, causing significant memory use and potential process termination due to out-of-memory (OOM) conditions. Remote attackers can trigger large transient memory spikes by including a long preamble in multipart/form-data requests. The impact scales with allowed request sizes and concurrency, potentially causing worker crashes or severe slowdown due to garbage collection. Versions 2.2.19, 3.1.17, and 3.2.2 enforce a preamble size limit (e.g., 16 KiB) or discard preamble data entirely. Workarounds include limiting total request body size at the proxy or web server level and monitoring memory and set per-process limits to prevent OOM conditions.","published":"2025-10-07T15:16:03.000Z","lastModified":"2026-10-19T16:10:00.000Z","status":"Analyzed","sourceIdentifier":"security-advisories@github.com","cvss":{"version":"3.1","score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"cwe":["CWE-400"],"affected":["rack/rack"],"epss":{"score":0.0093,"percentile":0.60416,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.93%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://github.com/rack/rack/commit/589127f4ac8b5cf11cf88fb0cd116ffed4d2181e","tags":["Patch"],"source":"security-advisories@github.com"},{"url":"https://github.com/rack/rack/commit/d869fed663b113b95a74ad53e1b5cae6ab31f29e","tags":["Patch"],"source":"security-advisories@github.com"},{"url":"https://github.com/rack/rack/commit/e08f78c656c9394d6737c022bde087e0f33336fd","tags":["Patch"],"source":"security-advisories@github.com"},{"url":"https://github.com/rack/rack/security/advisories/GHSA-p543-xpfm-54cp","tags":["Mitigation","Vendor Advisory"],"source":"security-advisories@github.com"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2025-61770","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}