What is CVE-2026-55203?

CVE-2026-55203 is a high-severity vulnerability in Haproxy, classified under Integer Overflow or Wraparound. CVSS score: 7.5/10. Published 2026-06-18.

How severe is CVE-2026-55203?

High severity. CVSS v3 base score is 7.5 out of 10.

Integer overflow in Haproxy

CVE-2026-55203

HAProxy through 3.4.0, fixed in commit 5985276, contains an integer overflow vulnerability in the fcgi_conn structure's drl field that allows buffer misparse as new FCGI record headers. When contentLength is 65535 and paddingLength is 1 or…

Vulnerability class: Integer Overflow

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N.

Affected products

Haproxy — versions 0, 5985276735777634d8c85f1d73bb7764aab0d6dd

Weakness classification (CWE)

CWE-190 — Integer Overflow or Wraparound

References

disclosure@vulncheck.com (patch)
disclosure@vulncheck.com (third-party-advisory)

Frequently asked questions

What is CVE-2026-55203?: CVE-2026-55203 is a high-severity vulnerability in Haproxy, classified under Integer Overflow or Wraparound. CVSS score: 7.5/10. Published 2026-06-18.
How severe is CVE-2026-55203?: High severity. CVSS v3 base score is 7.5 out of 10.