CVE-2026-55204

Name	CVE-2026-55204
Description	HAProxy through 3.4.0, fixed in commit 9a6d1fe, contains a null pointer dereference vulnerability in hpack_dht_insert() within src/hpack-tbl.c that fails to validate the return value of hpack_dht_defrag() when the memory pool is exhausted. An attacker can trigger HPACK dynamic table insertions under memory pressure to dereference a NULL pointer and crash HAProxy worker processes, causing denial of service.
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)
Debian Bugs	1140430

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
haproxy (PTS)	bullseye	2.2.9-2+deb11u6	vulnerable
	bullseye (security)	2.2.9-2+deb11u7	vulnerable
	bookworm, bookworm (security)	2.6.12-1+deb12u3	vulnerable
	trixie	3.0.11-1+deb13u2	vulnerable
	trixie (security)	3.0.11-1+deb13u3	vulnerable
	forky, sid	3.2.21-1	fixed

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

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
haproxy	source	experimental	3.4.1-1
haproxy	source	(unstable)	3.2.20-1			1140430

[trixie] - haproxy <no-dsa> (Minor issue)
https://github.com/haproxy/haproxy/commit/9a6d1fe3f00d86ab4ea6ea6ea0a5d48fc058a513