Back
CVE-2026-33555
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…
Medium4.0EPSS 0.31%
- Published
- Updated
- Reserved
- Assigned by
- mitre
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.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| mitreCNA (assigner) | 3.1 | Medium4.0 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N |
| NVDNVD · Modified | 3.1 | Medium5.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N |
- EPSS (exploitation in 30 days)
- 0.31% · top 76% of all CVEs (6 Nov 2026)
- CISA SSVC
- Exploitation: poc · Automatable: no · Technical impact: partial
Loading the EPSS history…
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 4.0.
Weakness
Affected products
References (6)
- https://www.haproxy.org (opens in a new tab)
- https://www.haproxy.com/documentation/haproxy-aloha/changelog/ (opens in a new tab)
- https://github.com/haproxy/haproxy/commit/05a295441c621089ffa4318daf0dbca2dd756a84 (opens in a new tab)
- https://www.mail-archive.com/[email protected]/msg46752.html (opens in a new tab)
- https://r3verii.github.io/cve/2026/04/14/haproxy-h3-standalone-fin-smuggling.html (opens in a new tab)exploit
- https://lists.debian.org/debian-lts-announce/2026/10/msg00036.html (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-33555)Record last updated .