CVE-2026-55204

Publication date 19 June 2026

Last updated 25 June 2026

Ubuntu priority

Cvss 3 Severity Score

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.

Status

Show unmaintained releases

Package	Ubuntu Release	Status
haproxy	26.04 LTS resolute	Fixed 3.2.9-1ubuntu2.2
	25.10 questing	Fixed 3.0.12-0ubuntu0.25.10.5
	24.04 LTS noble	Fixed 2.8.16-0ubuntu0.24.04.3
	22.04 LTS jammy	Fixed 2.4.30-0ubuntu0.22.04.2
	20.04 LTS focal	Needs evaluation
	18.04 LTS bionic	Needs evaluation
	16.04 LTS xenial	Needs evaluation

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
haproxy	Upstream: 9a6d1fe

Severity score breakdown

CVSS version:

Base score 8.7 · High

Base metrics

Parameter	Value
Attack vector	Network
Attack complexity	Low
Attack requirements	None
Privileges required	None
User interaction	None
Vulnerable system - Confidentiality impact	None
Vulnerable system - Integrity impact	None
Vulnerable system - Availability impact	High
Subsequent system - Confidentiality impact	None
Subsequent system - Integrity impact	None
Subsequent system - Availability impact	None

Scores

Parameter	Value
Base score	8.7 · High
Base + Threat score	-
Base + Environmental score	-
Base + Threat + Environmental score	-

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Base score 7.5 · High