CVE-2026-26962

Name	CVE-2026-26962
Description	Rack is a modular Ruby web server interface. From version 3.2.0 to before version 3.2.6, Rack::Multipart::Parser unfolds folded multipart part headers incorrectly. When a multipart header contains an obs-fold sequence, Rack preserves the embedded CRLF in parsed parameter values such as filename or name instead of removing the folded line break during unfolding. As a result, applications that later reuse those parsed values in HTTP response headers may be vulnerable to downstream header injection or response splitting. This issue has been patched in version 3.2.6.
Source	CVE (at NVD; CERT, ENISA, 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	fixed
	bullseye (security)	2.1.4-3+deb11u6	fixed
	bookworm	2.2.22-0+deb12u1	fixed
	bookworm (security)	2.2.22-0+deb12u2	fixed
	trixie (security), trixie	3.1.20-0+deb13u1	vulnerable
	forky	3.2.6-2	fixed
	sid	3.2.6-3	fixed

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

Package	Type	Release	Fixed Version
ruby-rack	source	experimental	3.2.6-1
ruby-rack	source	bullseye	(not affected)
ruby-rack	source	bookworm	(not affected)
ruby-rack	source	(unstable)	3.2.6-2

Notes

[bookworm] - ruby-rack <not-affected> (Vulnerable code introduced later)
[bullseye] - ruby-rack <not-affected> (Vulnerable code introduced later)
https://github.com/rack/rack/security/advisories/GHSA-rx22-g9mx-qrhv
Fixed by: https://github.com/rack/rack/commit/d50c4d3dab62fa80b2a276271d0d4fb338cfa7df (v3.2.6)