CVE-2026-55203
CRITICAL EPSS 23.8%
Published Jun 18, 20261w ago · Modified Jun 23, 20261w ago
9.0 CVSS 4.0
Published Jun 18, 2026 1w ago
Last Modified Jun 23, 2026 1w ago
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.
CVSS Details
Base Score
Exploitability
Impact
Vector string
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:L/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope X
Threat Intelligence
EPSS Exploit Probability
23.8% percentile
Exploit & Patch Status
No Known Exploit
No Patch Available
Weaknesses 1
CWE-190 Integer Overflow or Wraparound Numeric Error
References 2
- github.com https://github.com/haproxy/haproxy/commit/5985276735777634d8c85f1d73bb7764aab0d6dd
- vulncheck.com https://www.vulncheck.com/advisories/haproxy-integer-overflow-in-fcgi-demux-record-length-field
Remediation
No remediation data recorded yet
Check vendor advisories and the NVD entry for patch availability.