EUVD-2026-21997

| CVE-2026-33555 MEDIUM
2026-04-13 mitre GHSA-5mp8-rq5m-pj7m
Information Disclosure
4.0
CVSS 3.1
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CVSS VectorNVD

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N
Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
None
Integrity
Low
Availability
None

Lifecycle Timeline

2
patch_available
Apr 16, 2026 - 05:29 EUVD
3.3.6
Analysis Generated
Apr 13, 2026 - 17:14 vuln.today

DescriptionNVD

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.

AnalysisAI

HAProxy versions 2.6 through 3.3.5 fail to validate that received HTTP/3 message body lengths match the announced Content-Length header when streams close via empty-payload frames, enabling request smuggling and backend desynchronization attacks. An unauthenticated remote attacker can exploit this via network-level HTTP/3 traffic to cause integrity violations (integrity impact rated low by CVSS), though practical exploitation requires high attack complexity. …

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EUVD-2026-21997 vulnerability details – vuln.today
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