Traefik: BasicAuth middleware: timing side-channel vulnerability_CVE-2026-41263

6.3 / 10

MEDIUM

CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N

Description

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.

Basic Information

ID CVE-2026-41263

Source GitHub_M

Published Apr 30, 2026 at 20:39

Affected Product

Vendor traefik

Product traefik

Version < 2.11.43

Affected Versions traefik traefik < 2.11.43
traefik traefik >= 3.0.0-beta1, < 3.6.14
traefik traefik >= 3.7.0-ea.1, < 3.7.0-rc.2

CWE Classification

CWE-208

References

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