critical
CVE-2026-55203
haproxy: HAProxy: Response smuggling due to integer overflow in FastCGI record length handling
In the Trivy database since at least 24 Oct 2026, 07:11 UTCWhen it arrived before that build is not recorded.
Severity by source
NVD9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Red Hat7.5CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N
Bitnami9.0CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:L/SI:H/SA:N
Trivy's own label is CRITICAL. Rated critical by NVD, Bitnami. Rated lower by Red Hat (high), AlmaLinux (high), Azure Linux (high), Oracle (high), Rocky Linux (high), Ubuntu (medium).
Description
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.
Affected packages and fixed versions
| Source | Package | Fixed in |
|---|---|---|
| bitnami::Bitnami Vulnerability Database | haproxy | 2.4.36, 2.6.30, 2.8.25, 3.0.24, 3.2.20, 3.4.1 |
| alma 10 | haproxy | 3.0.5-6.el10_2.2 |
| alma 9 | haproxy | 2.8.14-3.el9_8.2 |
| Azure Linux 3.0 | haproxy | 0:2.9.11-7.azl3 |
| chainguard | haproxy-2.4, haproxy-2.6, haproxy-2.8 and 3 more | 2.4.36-r0 and 5 more |
| debian 11 | haproxy | no fix listed |
| debian 12 | haproxy | no fix listed |
| debian 13 | haproxy | no fix listed |
| debian 14 | haproxy | 3.2.20-1 |
| echo | haproxy | no fix listed |
| minimos | haproxy-2.6, haproxy-2.8, haproxy-3.0 and 2 more | 2.6.30-r0 and 4 more |
| Oracle Linux 9 | haproxy | 2.8.14-3.el9_8.2 |
Show all 49 entries from 34 sources
| Source | Package | Fixed in |
|---|---|---|
| bitnami::Bitnami Vulnerability Database | haproxy | 2.4.36, 2.6.30, 2.8.25, 3.0.24, 3.2.20, 3.4.1 |
| alma 10 | haproxy | 3.0.5-6.el10_2.2 |
| alma 9 | haproxy | 2.8.14-3.el9_8.2 |
| Azure Linux 3.0 | haproxy | 0:2.9.11-7.azl3 |
| chainguard | haproxy-2.4 | 2.4.36-r0 |
| chainguard | haproxy-2.6 | 2.6.31-r0 |
| chainguard | haproxy-2.8 | 2.8.26-r0 |
| chainguard | haproxy-3.0 | 3.0.24-r0 |
| chainguard | haproxy-3.2 | 3.2.20-r0 |
| chainguard | haproxy-3.3 | 3.3.11-r0 |
| debian 11 | haproxy | no fix listed |
| debian 12 | haproxy | no fix listed |
| debian 13 | haproxy | no fix listed |
| debian 14 | haproxy | 3.2.20-1 |
| echo | haproxy | no fix listed |
| minimos | haproxy-2.6 | 2.6.30-r0 |
| minimos | haproxy-2.8 | 2.8.25-r0 |
| minimos | haproxy-3.0 | 3.0.24-r0 |
| minimos | haproxy-3.2 | 3.2.20-r0 |
| minimos | haproxy-3.4 | 3.4.1-r0 |
| Oracle Linux 9 | haproxy | 2.8.14-3.el9_8.2 |
| rapidfort alma 10 | haproxy | 3.0.5-6.el10_2.2 |
| rapidfort alma 9 | haproxy | 2.8.14-3.el9_8.2 |
| rapidfort alpine 3.20 | haproxy | 3.0.24-r0 |
| rapidfort alpine 3.21 | haproxy | 3.0.24-r0 |
| rapidfort amazon linux 2023 | haproxy | 3.0.23-2.amzn2023.0.1 |
| rapidfort debian 12 | haproxy | 0:3.2.20-1 |
| rapidfort debian 13 | haproxy | 0:3.2.20-1 |
| rapidfort fedora 43 | haproxy | 3.0.24-1.fc43 |
| rapidfort Oracle Linux 10 | haproxy | 0:3.0.5-6.el10_2.2 |
| rapidfort Oracle Linux 9 | haproxy | 0:2.8.14-3.el9_8.2 |
| rapidfort rocky 9 | haproxy | 0:2.8.14-3.el9_8.2 |
| rapidfort ubuntu 20.04 | haproxy | 0:2.4.30-0ubuntu0.22.04.2, 0:2.8.16-0ubuntu0.24.04.3, 0:3.2.9-1ubuntu2.2 |
| rapidfort ubuntu 22.04 | haproxy | 0:2.4.30-0ubuntu0.22.04.2, 0:2.8.16-0ubuntu0.24.04.3, 0:3.2.9-1ubuntu2.2 |
| rapidfort ubuntu 24.04 | haproxy | 0:2.4.30-0ubuntu0.22.04.2, 0:2.8.16-0ubuntu0.24.04.3, 0:3.2.9-1ubuntu2.2 |
| Red Hat | haproxy | no fix listed |
| Red Hat | haproxy28 | no fix listed |
| Red Hat | rhceph-ci/haproxy | no fix listed |
| Red Hat | rhceph/rhceph-haproxy-rhel10 | no fix listed |
| Red Hat | rhceph/rhceph-haproxy-rhel8 | no fix listed |
| Red Hat | rhceph/rhceph-haproxy-rhel9 | no fix listed |
| rocky 10 | haproxy | 0.0.0 |
| rocky 9 | haproxy | 2.8.14-3.el9_8.2 |
| ubuntu 22.04 | haproxy | 2.4.30-0ubuntu0.22.04.2 |
| ubuntu 24.04 | haproxy | 2.8.16-0ubuntu0.24.04.3 |
| ubuntu 25.10 | haproxy | 3.0.12-0ubuntu0.25.10.5 |
| ubuntu 26.04 | haproxy | 3.2.9-1ubuntu2.2 |
| wolfi | haproxy-3.2 | 3.2.20-r0 |
| wolfi | haproxy-3.3 | 3.3.11-r0 |
References
- https://access.redhat.com/errata/RHSA-2026:55772
- https://access.redhat.com/security/cve/CVE-2026-55203
- https://bugzilla.redhat.com/2490518
- https://bugzilla.redhat.com/2490522
- https://bugzilla.redhat.com/show_bug.cgi?id=2490518
- https://bugzilla.redhat.com/show_bug.cgi?id=2490522
- https://creativecommons.org/licenses/by/4.0/
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-55203
All 18 references
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-55204
- https://errata.almalinux.org/9/ALSA-2026-55772.html
- https://errata.rockylinux.org/RLSA-2026:55772
- https://github.com/haproxy/haproxy/commit/5985276735777634d8c85f1d73bb7764aab0d6dd
- https://linux.oracle.com/cve/CVE-2026-55203.html
- https://linux.oracle.com/errata/ELSA-2026-55772.html
- https://nvd.nist.gov/vuln/detail/CVE-2026-55203
- https://ubuntu.com/security/notices/USN-8459-1
- https://www.cve.org/CVERecord?id=CVE-2026-55203
- https://www.vulncheck.com/advisories/haproxy-integer-overflow-in-fcgi-demux-record-length-field