What’s Vulnerable › Vulnerabilities

CVE-2026-88010: Traefik: BasicAuth singleflight coalescing reintroduces an unauthenticated username-enumeration timing oracle

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-22 · updated 2026-10-29
• Weakness: CWE-208

Description

Traefik is an open source HTTP reverse proxy and load balancer. From 3.6.11 until 3.7.13, checkPassword in pkg/middlewares/auth/basic_auth.go constructs the BasicAuth singleflight key from the submitted password and stored secret. Concurrent requests for absent usernames therefore coalesce on one key while configured usernames perform separate password hashes, creating an unauthenticated timing discrepancy that reveals whether a username exists. Sequential checks remain cost-equalized, Traefik v2 and Digest authentication are not affected, and the issue does not disclose credentials or bypass authentication. This issue is fixed in version 3.7.13.

Affected products

• Traefik: from 3.6.11 before 3.7.13 — fixed in 3.7.13
• Traefik: from 3.6.11, < 3.7.13

How to fix

Upgrade to a fixed version: Traefik 3.7.13. Check the vendor advisory for mitigations.

References

• https://github.com/traefik/traefik/commit/ddc1bf4660b85fd61fafdd821eb8216fb1a0b130
• https://github.com/traefik/traefik/pull/13816
• https://github.com/traefik/traefik/releases/tag/v3.7.13
• https://github.com/traefik/traefik/security/advisories/GHSA-8fcf-v89g-xpg6

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