USN-8459-1: HAProxy vulnerabilities

Publication date

22 June 2026

Overview

Several security issues were fixed in HAProxy.


Packages

  • haproxy - fast and reliable load balancing reverse proxy

Details

It was discovered that HAProxy incorrectly handled the FCGI demultiplexer
record length field. A remote attacker could possibly use this issue to
cause incorrect request routing, response smuggling, or other memory safety
issues. (CVE-2026-55203)

It was discovered that HAProxy failed to validate the return value of the
HPACK dynamic table defragmentation function when memory was exhausted. A
remote attacker could possibly use this issue to cause HAProxy to crash,
resulting in a denial of service. (CVE-2026-55204)

It was discovered that HAProxy incorrectly handled the FCGI demultiplexer
record length field. A remote attacker could possibly use this issue to
cause incorrect request routing, response smuggling, or other memory safety
issues. (CVE-2026-55203)

It was discovered that HAProxy failed to validate the return value of the
HPACK dynamic table defragmentation function when memory was exhausted. A
remote attacker could possibly use this issue to cause HAProxy to crash,
resulting in a denial of service. (CVE-2026-55204)

Update instructions

In general, a standard system update will make all the necessary changes.

Learn more about how to get the fixes.

The problem can be corrected by updating your system to the following package versions:

Ubuntu Release Package Version
26.04 LTS resolute haproxy –  3.2.9-1ubuntu2.2
25.10 questing haproxy –  3.0.12-0ubuntu0.25.10.5
24.04 LTS noble haproxy –  2.8.16-0ubuntu0.24.04.3
22.04 LTS jammy haproxy –  2.4.30-0ubuntu0.22.04.2

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