Threat Intelligence / CVE / CVE-2026-55203

CVE-2026-55203

CVSS 7.5 (HIGH) · Priority 3.8/10 · Published 2026-06-18

As of 2026-06-18, CVE-2026-55203 is a CVSS 7.5 (HIGH-severity) vulnerability. Threadlinqs Intelligence tracks 0 threats exploiting it.

Last updated: 2026-06-18

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 more, the drl field wraps to 0, causing incorrect record consumption and allowing malicious FastCGI backends to desynchronize the FCGI framing parser, potentially causing request routing errors, response smuggling, or memory safety issues.

CVSS v3 vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N

Weaknesses (CWE)

CWE-190

References

Full detection coverage & IOCs for threats exploiting CVE-2026-55203 are available via the Threadlinqs MCP server (Purple tier). View plans →

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Enriched from CVE.org, NVD (this product uses the NVD API but is not endorsed or certified by the NVD), FIRST EPSS, CISA KEV, and GitHub Security Advisories.