CVE-2026-88009: traefik HTTP Request/Response Smuggling

Vulnerability summary

CVE-2026-88009 is a high (CVSS 8.8) HTTP Request/Response Smuggling vulnerability in traefik. EPSS estimates a 0.44% chance of exploitation in the next 30 days, higher than 37.1% of scored vulnerabilities.

Timeline

1. 10-09-2026
   PublishedVulnerability first disclosed.
2. 10-09-2026
   Last modifiedVulnerability information updated.

Description

Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.57, and 3.7.13, Traefik accepts a rootless HTTP/1 request target that Go stores in URL.Opaque while leaving URL.Path empty. The rewriteRequestBuilder path evaluates routing, path sanitization, forwardAuth, encodedCharacters, and access logging against a path normalized to / but forwards URL.Opaque verbatim to the backend, allowing cross-vhost routing bypass, path-scoped authorization bypass, and access-log evasion when the backend interprets the opaque target as a path. This issue is fixed in 2.11.57 and 3.7.13.

• CWE-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.
• CWE-1286Improper Validation of Syntactic Correctness of InputThe product receives input that is expected to be well-formed - i.e., to comply with a certain syntax - but it does not validate or incorrectly validates that the input complies with the syntax.