CVE-2026-33555

A flaw was found in HAProxy. A remote attacker could exploit this vulnerability by sending a specially crafted HTTP/3 request. The HTTP/3 parser fails to verify that the received body length matches the announced content-length when a stream is closed with an empty payload. This desynchronization with the backend server can lead to request smuggling, allowing an attacker to bypass security mechanisms and potentially access unauthorized resources.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.