High [CVE-2026-88878] Denial of Service via HTTP/3 timeout bypass
This high-severity Red Hat Linux advisory covers CVE-2026-88878.
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Summary
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. A flaw was found in Traefik's HTTP/3 implementation (v2.8.2 through v2.11.55 and v3.0.0 through v3.7.11) where respondingTimeouts settings, specifically readTimeout, are not applied to QUIC streams.
In environments utilizing affected Traefik components, this allows attackers to exhaust bounded upstream backend connection pools, resulting in a denial of service for legitimate users. Red Hat severity: Important — CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
Weakness: CWE-770.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
Mitigation checklist
- Disable HTTP/3 on all Traefik entry points by removing the entryPoints.<name>.http3 configuration or setting enabled: false. Alternatively, enforce strict request body timeouts and connection limits at an upstream load balancer or network gateway.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
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