CVE-2026-33555

An issue was discovered in HAProxy before 3.3.6. The HTTP/3 parser does not check that the received body length matches a previously announced content-length when the stream is closed via a frame with an empty payload. This can cause desynchronization issues with the backend server and could be used for request smuggling. The earliest affected version is 2.6.

Affected products

Haproxy, Linuxmint, Ubuntu

Haproxy

< 3.3.6

Fix

Available

CVSS 3.1

5.8 MEDIUM

EPSS

0.3% (22th percentile)

Weakness

CWE-130

NVD status

Analyzed

Published

2026-04-13