HTTP Request Smuggling The advisory has been revoked - it doesn't affect any version of package haproxy (opens in a new tab)
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-RHEL10-HAPROXY-9838569
- published28 Apr 2025
- disclosed8 Sept 2021
Introduced: 8 Sep 2021
CVE-2021-40346 (opens in a new tab)Amendment
The Red Hat security team deemed this advisory irrelevant for RHEL:10.
NVD Description
Note: Versions mentioned in the description apply only to the upstream haproxy package and not the haproxy package as distributed by RHEL.
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.
References
- https://bugzilla.redhat.com/show_bug.cgi?id=2000599
- https://access.redhat.com/security/cve/CVE-2021-40346
- https://lists.apache.org/thread.html/r284567dd7523f5823e2ce995f787ccd37b1cc4108779c50a97c79120@%3Cdev.cloudstack.apache.org%3E
- https://lists.apache.org/thread.html/r8a58fd7a29808e5d27ee56877745e58dc4bb041b9af94601554e2a5a@%3Cdev.cloudstack.apache.org%3E
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/A7V2IYO22LWVBGUNZWVKNTMDV4KINLFO/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/MXTSBY2TEAXWZVFQM3CXHJFRONX7PEMN/
- https://www.mail-archive.com/haproxy@formilux.org
- https://www.mail-archive.com/haproxy@formilux.org/msg41114.html
- https://git.haproxy.org/?p=haproxy.git
- https://github.com/haproxy/haproxy/commit/3b69886f7dcc3cfb3d166309018e6cfec9ce2c95
- https://jfrog.com/blog/critical-vulnerability-in-haproxy-cve-2021-40346-integer-overflow-enables-http-smuggling/
- https://lists.apache.org/thread.html/r284567dd7523f5823e2ce995f787ccd37b1cc4108779c50a97c79120%40%3Cdev.cloudstack.apache.org%3E
- https://lists.apache.org/thread.html/r8a58fd7a29808e5d27ee56877745e58dc4bb041b9af94601554e2a5a%40%3Cdev.cloudstack.apache.org%3E
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/A7V2IYO22LWVBGUNZWVKNTMDV4KINLFO/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MXTSBY2TEAXWZVFQM3CXHJFRONX7PEMN/
- https://www.debian.org/security/2021/dsa-4968
- https://www.mail-archive.com/haproxy%40formilux.org
- https://www.mail-archive.com/haproxy%40formilux.org/msg41114.html
- https://github.com/donky16/CVE-2021-40346-POC