Bug 2531483 (CVE-2026-88004)

Summary: CVE-2026-88004 github.com/traefik/traefik: Traefik: Security bypass and identity spoofing via unsanitized request trailers
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: sdawley
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Traefik, an open-source HTTP reverse proxy and load balancer. Its entrypoint defenses, designed to sanitize header names, failed to inspect request trailers. This allowed an unauthenticated client to submit malicious header names within HTTP/1.1 chunked or HTTP/2 trailers. Consequently, these unsanitized trailer values could reach backend systems, bypassing security controls and potentially leading to identity spoofing or manipulation of routing data.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-09-10 15:00:57 UTC 
Traefik is an open source HTTP reverse proxy and load balancer. From 3.2.0 until 3.7.13, Traefik entrypoint defenses aliasHeadersStrategy, underscoreHeadersStrategy, and forwardedHeaders inspect req.Header but not req.Trailer, allowing an unauthenticated client to submit an aliasing or trusted header name in an HTTP/1.1 chunked trailer or an HTTP/2 trailer. When the retry or buffering middleware reads the body before the reverse proxy clones the request, the attacker-controlled trailer value reaches a backend that merges trailers into the header namespace, bypassing the documented delete or reject behavior and potentially spoofing identity or forwarded routing data. This issue is fixed in 3.7.13.