CVE-2026-55204

HIGH 7.5

HAProxy - NULL Pointer Dereference in hpack_dht_insert Function

CVSS Score

7.5

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-476
Vendor	haproxy
Product	haproxy
Published	Jun 18, 2026
Last Updated	Jun 18, 2026

Stay Ahead of the Next One

Get instant alerts for haproxy haproxy

Be the first to know when new high vulnerabilities affecting haproxy haproxy are published — delivered to Slack, Telegram or Discord.

Get Free Alerts → Free · No credit card · 60 sec setup

CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Affected Versions

haproxy / haproxy

0 ≤ 3.4.0

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/haproxy/haproxy/commit/9a6d1fe3f00d86ab4ea6ea6ea0a5d48fc058a513 vulncheck.com: https://www.vulncheck.com/advisories/haproxy-null-pointer-dereference-in-hpack-dht-insert-function

Credits

Tristan Madani (@TristanInSec)