# CVE-2026-33555: haproxy: An issue was discovered in HAProxy before 3.3.6

CVE-2026-33555 is fixed in 2 products on 1 platform, first by haproxy 2.8.16-0ubuntu0.24.04.2, released April 13, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-33555
- Priority: Routine
- CVSS: 5.8 (medium)
- EPSS: 0.0031
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Apr 13, 2026

## Description

An issue was discovered in HAProxy before 3.3.6. The HTTP/3 parser does not check that the received body length matches a previously announced content-length when the stream is closed via a frame with an empty payload. This can cause desynchronization issues with the backend server and could be used for request smuggling. The earliest affected version is 2.6.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | haproxy Debian 12.15 (bookworm) | 2.6.12-1+deb12u4 | [DEBIAN-CVE-2026-33555](https://patchblox.com/security/data/fix/linux/debian-cve-2026-33555.md) | Apr 13, 2026 |
| Linux | haproxy Debian 13.5 (trixie) | 3.0.11-1+deb13u3 | [DEBIAN-CVE-2026-33555](https://patchblox.com/security/data/fix/linux/debian-cve-2026-33555.md) | Apr 13, 2026 |
| Linux | haproxy Debian 14 | 3.2.15-1 | [DEBIAN-CVE-2026-33555](https://patchblox.com/security/data/fix/linux/debian-cve-2026-33555.md) | Apr 13, 2026 |
| Linux | haproxy Ubuntu 24.04.5 LTS (noble) | 2.8.16-0ubuntu0.24.04.2 | [haproxy 2.8.16-0ubuntu0.24.04.2](https://patchblox.com/security/data/fix/linux/ubuntu-noble-haproxy-2.8.16-0ubuntu0.24.04.2.md) | Apr 13, 2026 |
| Linux | haproxy Ubuntu 25.10 (questing) | 3.0.12-0ubuntu0.25.10.4 | [haproxy 3.0.12-0ubuntu0.25.10.4](https://patchblox.com/security/data/fix/linux/ubuntu-questing-haproxy-3.0.12-0ubuntu0.25.10.4.md) | Apr 13, 2026 |
| Linux | haproxy Ubuntu 26.04.1 LTS (resolute) | 3.2.9-1ubuntu2.1 | [haproxy 3.2.9-1ubuntu2.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-haproxy-3.2.9-1ubuntu2.1.md) | Apr 13, 2026 |
| Linux | haproxy opensuse-leap 16.0 | 3.2.15+git64.0fc44b458-160000.2.1 | [OPENSUSE-SU-2026:20618-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-20618-1.md) | Apr 23, 2026 |
| Linux | haproxy sles 15.6 | 2.8.11+git0.01c1056a4-150600.3.12.1 | [SUSE-SU-2026:1568-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-1568-1.md) | Apr 23, 2026 |
| Linux | haproxy sles 15.7 | 2.8.11+git0.01c1056a4-150600.3.12.1 | [SUSE-SU-2026:1568-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-1568-1.md) | Apr 23, 2026 |
| Linux | vim-haproxy Ubuntu 24.04.5 LTS (noble) | 2.8.16-0ubuntu0.24.04.2 | [vim-haproxy 2.8.16-0ubuntu0.24.04.2](https://patchblox.com/security/data/fix/linux/ubuntu-noble-vim-haproxy-2.8.16-0ubuntu0.24.04.2.md) | Apr 13, 2026 |
| Linux | vim-haproxy Ubuntu 25.10 (questing) | 3.0.12-0ubuntu0.25.10.4 | [vim-haproxy 3.0.12-0ubuntu0.25.10.4](https://patchblox.com/security/data/fix/linux/ubuntu-questing-vim-haproxy-3.0.12-0ubuntu0.25.10.4.md) | Apr 13, 2026 |
| Linux | vim-haproxy Ubuntu 26.04.1 LTS (resolute) | 3.2.9-1ubuntu2.1 | [vim-haproxy 3.2.9-1ubuntu2.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-vim-haproxy-3.2.9-1ubuntu2.1.md) | Apr 13, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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