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Vulnerability · Published Aug 6, 2026 · Assigned by GitHub_M

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

Low 2.1

In plain English

A low-severity improper authentication in traefik from traefik. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 27% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)2.1Low
Exploit odds (30 days)0.3%top 72.8% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

EcosystemPackageFixed inAdvisory
Gogithub.com/traefik/traefikno fix listedGO-2026-6204
Gogithub.com/traefik/traefik/v2no fix listedGO-2026-6204
Gogithub.com/traefik/traefik/v33.6.25GHSA-6765-c87h-8mrf
Gogithub.com/traefik/traefik/v33.7.10GHSA-6765-c87h-8mrf
Gogithub.com/traefik/traefik/v33.6.25, 3.7.10GO-2026-6204

Affected products (as reported)

VendorProductVersions
traefik traefik >= 3.6.11, < 3.6.25>= 3.7.0, < 3.7.10

Weakness: CWE-287 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

References