CVE intelligence

CVE-2026-33555

Vulnerability intelligence

Published Apr 13, 2026Sources checked Sep 27, 2026

5.8MEDIUMCVSS out of 10

What this means

Review the available evidence

CVE-2026-33555 and is rated Medium severity with a CVSS score of 5.8. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

CISA KEVNot listedBased on the latest collected catalog

EPSS0.6%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is 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.