What is CVE-2026-33555?

CVE-2026-33555 is a medium-severity vulnerability in Haproxy, classified under Improper Handling of Length Parameter Inconsistency. CVSS score: 4.0/10. Published 2026-04-13.

How severe is CVE-2026-33555?

Medium severity. CVSS v3 base score is 4.0 out of 10.

Is CVE-2026-33555 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Vulnerability in Haproxy

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 desyn…

EPSS: 0.000 (2.1th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 4.0 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N.

Affected products

Haproxy — versions 2.6

Weakness classification (CWE)

CWE-130 — Improper Handling of Length Parameter Inconsistency

Public proof-of-concept exploits

r3verii/CVE-2026-33555

References

Frequently asked questions

What is CVE-2026-33555?: CVE-2026-33555 is a medium-severity vulnerability in Haproxy, classified under Improper Handling of Length Parameter Inconsistency. CVSS score: 4.0/10. Published 2026-04-13.
How severe is CVE-2026-33555?: Medium severity. CVSS v3 base score is 4.0 out of 10.
Is CVE-2026-33555 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.