CVE-2026-33555
- State
- Published
- Severity
- 4.0 Medium
- Published
- Apr 13, 2026
- Updated
- Oct 18, 2026
- Reserved
- Mar 22, 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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 4.0 Medium | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N | mitre |
Weaknesses
- CWE-130 Improper Handling of Length Parameter Inconsistency
Affected Products
| Product | Versions |
|---|---|
HAProxyHAProxy |
|
References
- https://www.haproxy.org/
- https://www.haproxy.com/documentation/haproxy-aloha/changelog/
- https://github.com/haproxy/haproxy/commit/05a295441c621089ffa4318daf0dbca2dd756a84
- https://www.mail-archive.com/haproxy@formilux.org/msg46752.html
- https://r3verii.github.io/cve/2026/04/14/haproxy-h3-standalone-fin-smuggling.html
- https://lists.debian.org/debian-lts-announce/2026/10/msg00036.html
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