Information Exposure Through Timing Discrepancy in Traefik - CVE-2026-41263
Published: May 5, 2026
Vulnerability identifier: #VU129675
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-41263
CWE-ID: CWE-208
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Containous
Affected software:
Traefik
Traefik
Detailed vulnerability description
The vulnerability allows a remote attacker to enumerate valid usernames.
The vulnerability exists due to observable timing discrepancy in BasicAuth middleware when handling authentication requests. A remote attacker can send authentication attempts and measure response-time differences to enumerate valid usernames.
The issue occurs because the constant-time fallback secret resolves to an empty string, causing the comparison to short-circuit instead of performing a full bcrypt evaluation.
How to mitigate CVE-2026-41263
Install security update from vendor's website.