CVE-2026-55204: HAProxy - NULL Pointer Dereference in hpack_dht_insert Function
HAProxy - NULL Pointer Dereference in hpackdhtinsert Function
Other sources
HAProxy through 3.4.0, fixed in commit 9a6d1fe, contains a null pointer dereference vulnerability in hpackdhtinsert() within src/hpack-tbl.c that fails to validate the return value of hpackdhtdefrag() 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.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 2.9.11-7 - Upgrade
Upgrade
HAProxyto a version that resolves this vulnerability.Patch 9a6d1fe
Event History
Frequently Asked Questions
What is the severity of CVE-2026-55204?
The severity of CVE-2026-55204 is rated as high with a score of 7.5.
How do I fix CVE-2026-55204?
To fix CVE-2026-55204, update HAProxy to version 3.4.1 or later.
What impact does CVE-2026-55204 have on HAProxy?
CVE-2026-55204 allows an attacker to exploit a null pointer dereference in the hpack_dht_insert function, potentially leading to a denial-of-service condition.
Which versions of HAProxy are affected by CVE-2026-55204?
HAProxy versions prior to 3.4.1 are affected by CVE-2026-55204.
What type of vulnerability is CVE-2026-55204 classified as?
CVE-2026-55204 is classified as a Null Pointer Dereference vulnerability.