Bug 2531451 (CVE-2026-88878)

Summary: CVE-2026-88878 github.com/traefik/traefik: Traefik: Denial of Service via HTTP/3 timeout bypass
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: anjoseph, jprabhak, sdawley, wtam
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Traefik, an HTTP reverse proxy and load balancer. When HTTP/3 is enabled, an unauthenticated remote client can exploit a timeout bypass vulnerability by trickling request body bytes. This allows the client to hold a request open indefinitely, exhausting backend connection pools and leading to a denial of service (DoS) for legitimate users.
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Description OSIDB Bzimport 2026-09-10 13:24:08 UTC 
Traefik is an HTTP reverse proxy and load balancer. In versions >= v2.8.2 through <= v2.11.55 and >= v3.0.0 through <= v3.7.11, the entryPoints.<name>.transport.respondingTimeouts settings — notably readTimeout, which is enabled by default at 60s — are not applied to the HTTP/3 request path. readTimeout is enforced as a deadline on the underlying TCP connection, which cannot be applied to a QUIC stream, and Traefik's HTTP/3 server is constructed without any timeout. As a result, on entry points with HTTP/3 enabled, an unauthenticated remote client that trickles request body bytes can hold a request open indefinitely and, with it, one upstream connection per request, exhausting bounded backend connection pools and causing denial of service. The issue was introduced in v2.8.2 when a quic-go API change removed the embedded http.Server that carried these timeouts. Fixed in v2.11.56 and v3.7.12.