CVE-2026-77640

Name	CVE-2026-77640
Description	tor before 0.4.9.9 was prone to an infinite loop when decompressing a truncated zlib/gzip stream with done=1. A truncated stream never reaches Z_STREAM_END, causing zlib to return Z_BUF_ERROR with no input remaining, which buf_add_compress() mistook for a full output buffer and retried forever. Fixed by returning TOR_COMPRESS_ERROR in that case so the caller can abort cleanly. This is TROVE-2026-021.
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)
References	DSA-6372-1

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
tor (PTS)	bullseye (security), bullseye	0.4.5.16-1	vulnerable
	bookworm, bookworm (security)	0.4.9.11-0+deb12u1	fixed
	trixie (security), trixie	0.4.9.11-0+deb13u1	fixed
	forky, sid	0.4.9.11-1	fixed

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

Package	Type	Release	Fixed Version	Urgency	Origin
tor	source	bullseye	(unfixed)	end-of-life
tor	source	trixie	0.4.9.11-0+deb13u1		DSA-6372-1
tor	source	(unstable)	0.4.9.9-1

[bullseye] - tor <end-of-life> (see DSA 5562)
https://gitlab.torproject.org/tpo/core/tor/-/work_items/41274