CVE-2026-41263

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

Exploit odds

0.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-04-30 21:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 10:46 UTC Last updatedMost recent change to the record

Details

Published

2026-04-30 21:16 UTC

Last modified

2026-06-17 10:46 UTC

Exploit probability

0.4% · EPSS, next 30 days

Weakness

CWE-208

Record status

Analyzed

Affected

• Traefik < 2.11.43
• Traefik < 3.6.14
• Traefik 3.7.0

Attack profile CVSS 4.0 · 6.3

Attack vector

Network

Complexity

High

Attack requirements

None

Privileges needed

None

User interaction

None

Confidentiality

None

Integrity

None

Availability

None