CVE-2026-33555

Published: Apr 13, 2026Modified: Jun 29, 2026

5.8

Vector

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

Exploitability: 3.9 / Impact: 1.4

Source: NVD

Description

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 (1)

Products: Haproxy: Haproxy

1 product

Configuration A

1 vulnerable

Vulnerable Software	Affected Versions
Haproxy Haproxy	From 2.6.0 to 3.3.6

Related CWEs

Improper Handling of Length Parameter Inconsistency

The product parses a formatted message or structure, but it does not handle or incorrectly handles a length field that is inconsistent with the actual length of the associated data.

References (6)

https://github.com/haproxy/haproxy/commit/05a295441c621089ffa4318daf0dbca2dd756a84

Source: cve@mitre.org

Patch

https://r3verii.github.io/cve/2026/04/14/haproxy-h3-standalone-fin-smuggling.html

Source: cve@mitre.org

ExploitThird Party Advisory

https://www.haproxy.com/documentation/haproxy-aloha/changelog/

Source: cve@mitre.org

Release Notes

https://www.haproxy.org

Source: cve@mitre.org

Product

https://www.mail-archive.com/haproxy@formilux.org/msg46752.html

Source: cve@mitre.org

Release Notes

https://r3verii.github.io/cve/2026/04/14/haproxy-h3-standalone-fin-smuggling.html

Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0

ExploitThird Party Advisory

Timeline

No history available yet.