What is CVE-2026-55203?

CVE-2026-55203 is a security advisory published by Microsoft Security Response Center (MSRC) with High severity. HAProxy - Integer Overflow in FCGI Demux Record Length Field

Which CVE IDs does CVE-2026-55203 cover?

CVE-2026-55203 covers the following CVE IDs: CVE-2026-55203. Each CVE has its own detail page on EchelonGraph Pulse with the synthesized EG score.

What is the CVSS v3 score of CVE-2026-55203?

CVE-2026-55203 has a CVSS v3 base score of 7.5, published by Microsoft Security Response Center (MSRC).

Which products are affected by CVE-2026-55203?

CVE-2026-55203 affects 2 products, including: azl3 haproxy 2.9.11-6 on Azure Linux 3.0; azl3 haproxy 2.9.11-7 on Azure Linux 3.0.

CVE-2026-55203HighCVSS 7.5

HAProxy - Integer Overflow in FCGI Demux Record Length Field

Vendor

Microsoft Security Response Center (MSRC)

Published

June 30, 2026

Last Modified

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🔗 CVE IDs covered (1)

CVE-2026-55203 →

🎯 Affected products2

azl3 haproxy 2.9.11-6 on Azure Linux 3.0
azl3 haproxy 2.9.11-7 on Azure Linux 3.0

✅ Remediation

KBCBL-Mariner Releases (Security Update) — fixed build 2.9.11-7

🔗 References (2)

advisoryhttps://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55203
referencehttps://learn.microsoft.com/en-us/azure/azure-linux/tutorial-azure-linux-upgrade