Medium severity4.0NVD Advisory· Published Apr 13, 2026· Updated Apr 22, 2026

CVE-2026-33555

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.

Affected products

Haproxy/Haproxyreferences

Patches

No patches discovered yet.

Vulnerability mechanics

AI mechanics synthesis has not run for this CVE yet.

References

github.com/haproxy/haproxy/commit/05a295441c621089ffa4318daf0dbca2dd756a84nvd
r3verii.github.io/cve/2026/04/14/haproxy-h3-standalone-fin-smuggling.htmlnvd
www.haproxy.com/documentation/haproxy-aloha/changelog/nvd
www.haproxy.orgnvd
www.mail-archive.com/haproxy@formilux.org/msg46752.htmlnvd

News mentions

No linked articles in our index yet.

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