CVE-2026-55203

Description

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.

References

https://www.vulncheck.com/advisories/haproxy-integer-overflow-in-fcgi-demux-record-length-field

https://github.com/haproxy/haproxy/commit/5985276735777634d8c85f1d73bb7764aab0d6dd

Details

Source: Mitre, NVD

Risk Information

CVSS v2

CVSS v3

CVSS v4