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.

Attack Vector Network

Attack Complexity High

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact None

Subsequent System Confidentiality Impact Low

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

No CVSS v3.1

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
traefik traefik affected
Version Status Constraints
< 2.11.43 affected —
>= 3.0.0-beta1, < 3.6.14 affected —
>= 3.7.0-ea.1, < 3.7.0-rc.2 affected —

No data.

No data.

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Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/traefik/traefik/releases/tag/v2.11.43 cve-icon cve-icon
https://github.com/traefik/traefik/releases/tag/v3.6.14 cve-icon cve-icon
https://github.com/traefik/traefik/releases/tag/v3.7.0-rc.2 cve-icon cve-icon
https://github.com/traefik/traefik/security/advisories/GHSA-6x2q-h3cr-8j2h cve-icon cve-icon
History

Thu, 30 Apr 2026 21:45:00 +0000

Type Values Removed Values Added
First Time appeared Traefik
Traefik traefik
Vendors & Products Traefik
Traefik traefik

Thu, 30 Apr 2026 20:45:00 +0000

Type Values Removed Values Added
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.
Title Traefik: BasicAuth middleware: timing side-channel vulnerability
Weaknesses CWE-208
References
Metrics cvssV4_0

{'score': 6.3, 'vector': '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'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-04-30T20:39:49.658Z

Reserved: 2026-04-18T14:01:46.801Z

Link: CVE-2026-41263

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-04-30T21:16:33.390

Modified: 2026-04-30T21:16:33.390

Link: CVE-2026-41263

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-04-30T21:30:36Z

Weaknesses