CVE-2026-33555
CVSS Score
4.0
EPSS Score
0.0%
EPSS Percentile
1th
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.
| CWE | CWE-130 |
| Vendor | haproxy |
| Product | haproxy |
| Published | Apr 13, 2026 |
| Last Updated | Apr 22, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N Attack Vector
Attack Complexity
Privileges Required
User Interaction
Scope
Confidentiality
Integrity
Availability
Affected Versions
HAProxy / HAProxy
2.6 < 3.3.6
References
haproxy.org: https://www.haproxy.org haproxy.com: https://www.haproxy.com/documentation/haproxy-aloha/changelog/ github.com: https://github.com/haproxy/haproxy/commit/05a295441c621089ffa4318daf0dbca2dd756a84 mail-archive.com: https://www.mail-archive.com/[email protected]/msg46752.html r3verii.github.io: https://r3verii.github.io/cve/2026/04/14/haproxy-h3-standalone-fin-smuggling.html