Disclosure summary
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.
Source-reported weakness categories
CWE-190
Source-specific records & product guidance
Sources retain their own attribution and scoring. Follow the original record to confirm affected versions, fixed releases, and configuration conditions.
NIST National Vulnerability Database · NVD-CVE-2026-55203
Open original source · Updated Oct 08, 2026
Only CPE matches marked vulnerable=true are indexed. AND/OR platform conditions must be checked in the original NVD record.
| Vendor | Product / association | Version / bounds |
|---|---|---|
| haproxy | haproxy | * {"versionStartIncluding":"3.3","versionEndExcluding":"3.4.1"} |
Original records & references
- NIST NVD record
- CVE Program record
- github.com — Patch
- www.vulncheck.com — Third Party Advisory
PUBLISHED 2026-06-18T13:16:34-04:00
MODIFIED 2026-10-08T13:12:58-04:00
INGESTED 2026-10-10T20:50:35-04:00