Bug 2501068

Summary: CVE-2026-55203 haproxy: HAProxy: Response smuggling due to integer overflow in FastCGI record length handling [fedora-all]
Product: [Fedora] Fedora Reporter: Ganesh <gnaik>
Component: haproxyAssignee: Robert Scheck <redhat-bugzilla>
Status: CLOSED RAWHIDE QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: high Docs Contact:
Priority: high    
Version: rawhideCC: redhat-bugzilla
Target Milestone: ---Keywords: Security, SecurityTracking
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard: {"flaws": ["94733e17-0dee-4150-961d-f84ab538a46b"]}
Fixed In Version: haproxy-3.4.1-1.fc45 Doc Type: ---
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2026-07-29 22:43:14 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 2490522    

Description Ganesh 2026-07-15 18:13:57 UTC 
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

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.
Comment 1 Robert Scheck 2026-07-29 22:43:14 UTC 
HAProxy 3.4.1 was submitted to Fedora Rawhide nearly 3 weeks before this report was filed.