Bug 2490522 (CVE-2026-55203) - CVE-2026-55203 haproxy: HAProxy: Response smuggling due to integer overflow in FastCGI record length handling
Summary: CVE-2026-55203 haproxy: HAProxy: Response smuggling due to integer overflow i...
Keywords:
Status: NEW
Alias: CVE-2026-55203
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 2501068
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-06-18 17:02 UTC by OSIDB Bzimport
Modified: 2026-08-17 18:38 UTC (History)
12 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2026:55679 0 None None None 2026-08-17 15:00:46 UTC
Red Hat Product Errata RHSA-2026:55772 0 None None None 2026-08-17 16:59:34 UTC
Red Hat Product Errata RHSA-2026:55800 0 None None None 2026-08-17 17:20:05 UTC
Red Hat Product Errata RHSA-2026:55801 0 None None None 2026-08-17 17:45:26 UTC
Red Hat Product Errata RHSA-2026:55802 0 None None None 2026-08-17 17:50:21 UTC
Red Hat Product Errata RHSA-2026:55803 0 None None None 2026-08-17 18:38:41 UTC

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
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