CVE-2026-88878

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CVE-2026-88878

Summary: Traefik v2.8.2 through v3.6 HTTP/3 Timeout Bypass

Details: 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.

References: https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/88xxx/CVE-2026-88878.json, https://github.com/traefik/traefik/security/advisories/GHSA-7ghq-v6jf-g56c, https://nvd.nist.gov/vuln/detail/CVE-2026-88878, https://www.vulncheck.com/advisories/traefik-2.8.2-through-3.6-http-3-timeout-bypass