CVE-2026-88878
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HTTP/3 Request Timeout Bypass in Traefik

Publication date: 2026-09-10

Last updated on: 2026-09-10

Assigner: VulnCheck

Description
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.

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Meta Information

Published
2026-09-10
Last Modified
2026-09-10
Generated
2026-09-10
AI Q&A
2026-09-10
EPSS Evaluated
N/A
NVD
CVE-2026-88878
EUVD
EUVD-2026-75428

Affected Vendors & Products

Showing 6 associated CPEs
Vendor Product Version / Range
traefik traefik to 2.11.56 (inc)
traefik traefik to 3.7.12 (inc)
traefik traefik From 2.8.2 (inc) to 2.11.55 (inc)
traefik traefik From 3.0.0 (inc) to 3.7.11 (inc)
traefik traefik 2.11.56
traefik traefik 3.7.12

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-770 The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

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Executive Summary

CVE-2026-88878 is a timeout bypass vulnerability in Traefik, a reverse proxy and load balancer. When HTTP/3 is enabled, the readTimeout setting (default 60 seconds) is not enforced for HTTP/3 requests. This allows unauthenticated clients to trickle request data, keeping connections open indefinitely and exhausting backend connection pools.

Detection Guidance

To detect this vulnerability, check if Traefik is running a vulnerable version (2.8.2 to 2.11.55 or 3.0.0 to 3.7.11) with HTTP/3 enabled. Verify the version using commands like 'traefik version' or by inspecting the Traefik configuration file. Check logs for unusually long-held HTTP/3 connections or connection pool exhaustion events.

Impact Analysis

This vulnerability can lead to denial-of-service attacks. Attackers can consume all available connections in backend services by holding HTTP/3 requests open indefinitely, causing service disruptions or crashes. Systems relying on Traefik with HTTP/3 enabled are particularly at risk.

Compliance Impact

This vulnerability could indirectly impact compliance with GDPR and HIPAA by enabling denial-of-service attacks that disrupt service availability. GDPR requires data processing systems to ensure availability and resilience, while HIPAA mandates safeguards against service disruptions that could affect protected health information access. Exhausted connection pools may lead to service unavailability, potentially violating these requirements.

Mitigation Strategies

Upgrade Traefik to a patched version (v2.11.56 or v3.7.12 or later) immediately. If upgrading is not possible, disable HTTP/3 in the Traefik configuration by removing or commenting out the HTTP/3 transport settings. Monitor connection pools and network traffic for signs of exploitation.

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