CVE-2026-41263

Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.43, 3.6.14, and 3.7.0-rc.2, there is a timing side-channel vulnerability in Traefik's BasicAuth middleware that allows an attacker to enumerate valid usernames through response-time differences. The variable intended to hold a constant-time fallback secret always resolves to an empty string, causing the constant-time comparison to short-circuit in microseconds rather than performing a full bcrypt evaluation. This restores the original timing oracle and makes it possible to distinguish existing users from non-existing ones by measuring authentication response times. This issue has been patched in versions 2.11.43, 3.6.14, and 3.7.0-rc.2.

• CWE-208

• https://github.com/traefik/traefik/releases/tag/v2.11.43Product, Release Notes
• https://github.com/traefik/traefik/releases/tag/v3.6.14Product, Release Notes
• https://github.com/traefik/traefik/releases/tag/v3.7.0-rc.2Product, Release Notes
• https://github.com/traefik/traefik/security/advisories/GHSA-6x2q-h3cr-8j2hPatch, Vendor Advisory

Published

Apr 30, 2026

Last Modified

Jun 17, 2026

Status

Analyzed

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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