What’s Vulnerable › Vulnerabilities

CVE-2026-71326: Traefik: BasicAuth singleflight key collision allows authenticated identity spoofing

• Severity: low (CVSS 3.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-06 · updated 2026-09-16
• Weakness: CWE-287

Description

Traefik is an open source HTTP reverse proxy and load balancer. From 3.6.11 until 3.6.25 and 3.7.10, Traefik's BasicAuth middleware in pkg/middlewares/auth/basic_auth.go deduplicates concurrent password checks with a singleflight key built from the delimiter-free concatenation of password and secret, allowing an attacker who has a valid credential and the stored hash to authenticate as an unconfigured username when headerField trusts the forwarded identity. This issue is fixed in 3.6.25 and 3.7.10.

Affected products

• Traefik: from 3.6.11 before 3.6.25; from 3.7.0 before 3.7.10 — fixed in 3.6.25, 3.7.10

How to fix

Upgrade to a fixed version: Traefik 3.6.25, 3.7.10. Check the vendor advisory for mitigations.

References

• https://github.com/traefik/traefik/commit/b5ace8eb5d6779980567f5e75efd2d9e08b7e350
• https://github.com/traefik/traefik/pull/13572
• https://github.com/traefik/traefik/releases/tag/v3.6.25
• https://github.com/traefik/traefik/releases/tag/v3.7.10
• https://github.com/traefik/traefik/security/advisories/GHSA-6765-c87h-8mrf

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