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CVE-2026-33555

MediumCVSS 4 / 10
Published Apr 13, 2026·Last modified Jul 8, 2026
Affected Components(115)
haproxy/haproxy
2.9-dev10
haproxy/haproxy
3.1-dev11
haproxy/haproxy
3.2-dev5
1 / 39
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.

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Risk Scores
Base Score
4.0

The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The vulnerability can affect other systems as well, not just the initial system. There is a low impact on the integrity of the data.

Threat Intelligence
3.8

Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.

EPSS
0.30%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Proof of Concept

A proof of concept is available for this vulnerability (1 exploit found).

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