Threat Intelligence Database

An issue was discovered in HAProxy 3.3.0 through 3.4.4 and in 3.5-dev1 through 3.5-dev5. Exploitation requires an HTTP/3 frontend: HAProxy must be built with QUIC support and configured with a QUIC bind listener, and the affected traffic must reach a backend over HTTP/1.1 using chunked transfer coding on a reused connection. Under those conditions, when an HTTP/3 request carries no Content-Length header, the HTTP/3 multiplexer credits the length declared in a DATA frame header to the stream endpoint's known-input-payload estimate at the moment the frame header is decoded, before the payload has been received, and that declared length is emitted verbatim as the HTTP/1.1 chunk size. A remote unauthenticated client that declares more payload than it delivers and then ends the stream causes HAProxy to announce a chunk larger than the bytes it writes and to return the connection to the idle pool in a desynchronized state. The result is potential HTTP request smuggling on reused backend connections: an attacker can place a request past a frontend rule such as a path-based http-request deny, so that the smuggled request is never seen by HAProxy's HTTP analysis, and can cause concurrent clients' requests, including their request lines and Authorization headers, to be consumed as the attacker's request body and lost. Exploitation is not deterministic; it depends on a race with backend connection pooling, succeeding in a majority of but not all trials during testing, and can be retried freely. The mechanism was introduced in 3.3-dev10; releases 3.2.x and earlier are unaffected.

HAProxy Community Edition versions 3.0 through 3.3 before 3.3.3 have a vulnerability due to the lack of a length check for the NEW_TOKEN format. This issue also affects HAProxy Enterprise and ALOHA editions. The vulnerability is identified as CWE-130 and is classified with medium severity.

Red Hat has released a security advisory for Red Hat Hardened Images RPMs, including an update to haproxy version 3.0.25-0.1.1.hum1 for aarch64 and x86_64 architectures. This update addresses vulnerabilities identified by CVE-2026-26080 and CVE-2026-26081. The advisory indicates that a patch is available to fix these issues. The update is part of a bug fix and enhancement release for the affected RPMs.

Inefficient algorithm complexity in mjson in HAProxy allows remote attackers to cause a denial of service via specially crafted JSON requests.

HighVulnerabilityGermanyFranceNetherlands+3#cve#cve-2025-11230#cwe-407

QUIC in HAProxy 3.1.x before 3.1-dev7, 3.0.x before 3.0.5, and 2.9.x before 2.9.11 allows opening a 0-RTT session with a spoofed IP address. This can bypass the IP allow/block list functionality.

MediumVulnerabilityUnited StatesGermanyFrance+7#cve#cve-2024-49214