CVE-2021-40346

medium

Published — · Modified —

CVSS v3

—

CVSS v2

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VIR risk

5.5

Description

An integer overflow exists in HAProxy 2.0 through 2.5 in htx_add_header that can be exploited to perform an HTTP request smuggling attack, allowing an attacker to bypass all configured http-request HAProxy ACLs and possibly other ACLs.

Predictions

Exploit likelihood

20%

Patch ETA

—

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

vendor Authored 2026-05-27

Vendor advisory: debian — https://security-tracker.debian.org/tracker/CVE-2021-40346

vendor Authored 2026-05-27

Vendor advisory: suse — https://www.suse.com/security/cve/CVE-2021-40346.html

OS impact

OS	Version	Status	Fixed in
arch		fixed	`2.4.4-1`
sles		affected
debian	bookworm	fixed	`2.2.16-3`
debian	bullseye	fixed	`2.2.9-2+deb11u2`
debian	forky	fixed	`2.2.16-3`
debian	sid	fixed	`2.2.16-3`
debian	trixie	fixed	`2.2.16-3`

References

https://www.suse.com/security/cve/CVE-2021-40346.html
https://security-tracker.debian.org/tracker/CVE-2021-40346

Verify integrity in audit chain (admin only). AS-IS.