CVE-2025-61770

Name	CVE-2025-61770
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.
Source	CVE (at NVD; CERT, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
ruby-rack (PTS)	bullseye	2.1.4-3+deb11u2	vulnerable
	bullseye (security)	2.1.4-3+deb11u3	vulnerable
	bookworm, bookworm (security)	2.2.13-1~deb12u1	vulnerable
	forky, sid, trixie	3.1.16-0.1	vulnerable

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
ruby-rack	source	(unstable)	(unfixed)

Notes

https://github.com/rack/rack/security/advisories/GHSA-p543-xpfm-54cp
Fixed by: https://github.com/rack/rack/commit/589127f4ac8b5cf11cf88fb0cd116ffed4d2181e (v3.2.2)
Fixed by: https://github.com/rack/rack/commit/e08f78c656c9394d6737c022bde087e0f33336fd (v3.1.17)
Fixed by: https://github.com/rack/rack/commit/d869fed663b113b95a74ad53e1b5cae6ab31f29e (v2.2.19)