HAProxy - Integer Overflow in FCGI Demux Record Length Field
CVE-2026-55203 is fixed in 2 products on 1 platform, first by RHSA-2026:55800, released June 18, 2026. It is not reported as exploited. Patch Radar priority: High.
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.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Linux | |||
| haproxy · Debian 14 | 3.2.20-1 | DEBIAN-CVE-2026-55203 | Jun 29, 2026 |
| haproxy · RHEL 10 | 3.0.5-4.el10_0.3 | RHSA-2026:55800 | Jun 18, 2026 |
| haproxy · RHEL 9 | 0:2.8.14-3.el9_8.2 | RHSA-2026:55772 | Aug 19, 2026 |
| haproxy · Ubuntu 22.04.1 LTS (jammy) | 2.4.30-0ubuntu0.22.04.2 | haproxy 2.4.30-0ubuntu0.22.04.2 | Jun 24, 2026 |
| haproxy · Ubuntu 24.04.5 LTS (noble) | 2.8.16-0ubuntu0.24.04.3 | haproxy 2.8.16-0ubuntu0.24.04.3 | Jun 24, 2026 |
| haproxy · Ubuntu 25.10 (questing) | 3.0.12-0ubuntu0.25.10.5 | haproxy 3.0.12-0ubuntu0.25.10.5 | Jun 24, 2026 |
| haproxy · Ubuntu 26.04.1 LTS (resolute) | 3.2.9-1ubuntu2.2 | haproxy 3.2.9-1ubuntu2.2 | Jun 18, 2026 |
| haproxy · almalinux 10 | 3.0.5-6.el10_2.2 | ALSA-2026:55679 | Aug 17, 2026 |
| haproxy · almalinux 9 | 2.8.14-3.el9_8.2 | ALSA-2026:55772 | Aug 17, 2026 |
| haproxy · ol 10 | 0:3.0.5-6.el10_2.2 | ELSA-2026-55679 | Aug 17, 2026 |
| haproxy · ol 9 | 0:2.8.14-3.el9_8.2 | ELSA-2026-55772 | Aug 17, 2026 |
| haproxy · opensuse-leap 16.0 | 3.2.21+git0.dbe43be37-160000.1.1 | OPENSUSE-SU-2026:21245-1 | Jul 7, 2026 |
| haproxy · rocky 10 | 0:3.0.5-6.el10_2.2 | RLSA-2026:55679 | Aug 18, 2026 |
| haproxy · rocky 9 | 0:2.8.14-3.el9_8.2 | RLSA-2026:55772 | Aug 18, 2026 |
| haproxy · sles 15.6 | 2.8.11+git0.01c1056a4-150600.3.15.1 | SUSE-SU-2026:2652-1 | Jun 26, 2026 |
| haproxy · sles 15.7 | 2.8.11+git0.01c1056a4-150600.3.15.1 | SUSE-SU-2026:2652-1 | Jun 26, 2026 |
| haproxy · sles 16.0 | 3.2.21+git0.dbe43be37-160000.1.1 | SUSE-SU-2026:22557-1 | Jul 7, 2026 |
| vim-haproxy · Ubuntu 22.04.1 LTS (jammy) | 2.4.30-0ubuntu0.22.04.2 | vim-haproxy 2.4.30-0ubuntu0.22.04.2 | Jun 24, 2026 |
| vim-haproxy · Ubuntu 24.04.5 LTS (noble) | 2.8.16-0ubuntu0.24.04.3 | vim-haproxy 2.8.16-0ubuntu0.24.04.3 | Jun 24, 2026 |
| vim-haproxy · Ubuntu 25.10 (questing) | 3.0.12-0ubuntu0.25.10.5 | vim-haproxy 3.0.12-0ubuntu0.25.10.5 | Jun 24, 2026 |
| vim-haproxy · Ubuntu 26.04.1 LTS (resolute) | 3.2.9-1ubuntu2.2 | vim-haproxy 3.2.9-1ubuntu2.2 | Jun 18, 2026 |
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