Ubuntu 26.04 LTS HAProxy Important Denial of Service USN-8459-1

ubuntu

June 22, 2026

Several security issues were fixed in HAProxy.

Summary

Several security issues were fixed in HAProxy.

Software Description:

- 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)

Topics Covered

security advisory denial of service Ubuntu important haproxy request routing

Update Instructions

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

Ubuntu 26.04 LTS
  haproxy                         3.2.9-1ubuntu2.2

Ubuntu 25.10
  haproxy                         3.0.12-0ubuntu0.25.10.5

Ubuntu 24.04 LTS
  haproxy                         2.8.16-0ubuntu0.24.04.3

Ubuntu 22.04 LTS
  haproxy                         2.4.30-0ubuntu0.22.04.2

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