Bug 2490522 (CVE-2026-55203)

Summary: CVE-2026-55203 haproxy: HAProxy: Response smuggling due to integer overflow in FastCGI record length handling
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: amctagga, aoconnor, bniver, flucifre, gmeno, groman, mbenjamin, mhackett, rhel-process-autobot, sostapov, vereddy, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in HAProxy. A malicious FastCGI (Fast Common Gateway Interface) backend can exploit an integer overflow vulnerability in the fcgi_conn structure's drl field. This occurs when specific contentLength and paddingLength values cause the drl field to wrap to zero, leading to incorrect record consumption. This desynchronizes the FCGI framing parser, potentially resulting in response smuggling, request routing errors, or memory safety issues.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 2501068    
Bug Blocks:    

Description OSIDB Bzimport 2026-06-18 17:02:24 UTC
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 5 errata-xmlrpc 2026-08-17 15:00:45 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:55679 https://access.redhat.com/errata/RHSA-2026:55679

Comment 6 errata-xmlrpc 2026-08-17 16:59:33 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:55772 https://access.redhat.com/errata/RHSA-2026:55772

Comment 7 errata-xmlrpc 2026-08-17 17:20:03 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10.0 Extended Update Support

Via RHSA-2026:55800 https://access.redhat.com/errata/RHSA-2026:55800

Comment 8 errata-xmlrpc 2026-08-17 17:45:25 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions

Via RHSA-2026:55801 https://access.redhat.com/errata/RHSA-2026:55801

Comment 9 errata-xmlrpc 2026-08-17 17:50:20 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions

Via RHSA-2026:55802 https://access.redhat.com/errata/RHSA-2026:55802

Comment 10 errata-xmlrpc 2026-08-17 18:38:40 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.6 Extended Update Support

Via RHSA-2026:55803 https://access.redhat.com/errata/RHSA-2026:55803