CVE-2026-55204

High

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.

SeverityHigh

CVSS7.5

Exploit probability—

ProductHaproxy

PublishedJun 18, 2026

First seenJun 18, 2026

Weakness typeCWE-476NULL pointer dereference

How to fix

Update

haproxy haproxy2.4.36, 2.6.30, 2.8.25, 3.0.24, 3.2.20, 3.4.1 or later

Patches

github.com/haproxy/haproxy/commit/9a6d1fe3f00d86ab4ea6ea6ea0a5d48fc058a513

Affected products

Product	Affected versions	Fixed in
haproxy haproxy	v < 2.4.36, 2.5 ≤ v < 2.6.30, 2.7 ≤ v < 2.8.25, 2.9 ≤ v < 3.0.24, 3.1 ≤ v < 3.2.20, 3.3 ≤ v < 3.4.1	2.4.36, 2.6.30, 2.8.25, 3.0.24, 3.2.20, 3.4.1

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