CVE-2026-71326 Traefik: BasicAuth singleflight key collision allows authenticated identity spoofing
Traefik's BasicAuth middleware allows authenticated users to spoof identities due to a singleflight key collision, enabling unauthorized access when headerField is trusted.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-71326?
CVE-2026-71326 is a low-severity authentication bypass vulnerability in Traefik Traefik, published on 6 Aug 2026. An attacker needs administrator access to exploit it, with no action from the victim.
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.
Weakness: CWE-287
Which versions are affected by CVE-2026-71326?
7 open source packages ship an affected version, including github.com/traefik/traefik/v3, github.com/traefik/traefik and github.com/traefik/traefik/v2. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/traefik/traefik/v3 Go | From 3.6.11 | 3.6.25, 3.7.10 |
github.com/traefik/traefik/v3 Go | From 3.6.11 | 3.6.25 |
github.com/traefik/traefik/v3 Go | From 3.6.11 | 3.6.25 |
github.com/traefik/traefik/v3 Go | From 3.7.0 | 3.7.10 |
github.com/traefik/traefik/v3 Go | From 3.7.0 | 3.7.10 |
github.com/traefik/traefik Go | All versions | None |
1 more packages
github.com/traefik/traefik/v2 Go | All versions | None |
Products include Traefik Traefik.
How do I fix CVE-2026-71326?
Upgrade github.com/traefik/traefik/v3 to a fixed version for your release line: 3.6.25 or 3.7.10.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-71326 being exploited?
There is no known exploitation of CVE-2026-71326 in the wild and no public exploit code.
Other vulnerabilities in Traefik Traefik
- CVE-2024-45410 HTTP client can remove the X-Forwarded headers in Traefik
- CVE-2026-88877 Traefik v3.7.0 Authentication Bypass via from-to-www-redirect
- CVE-2026-85595 Traefik before v2.11.55 and v3.0.0 through v3.7.10 Authentication Bypass via digestAuth
- CVE-2026-88007 Traefik HTTP/3 Backend NTLM Connection Reuse
- CVE-2026-88009 Traefik: Rootless HTTP/1 request-target routes as "/" but is forwarded verbatim, bypassing path-scoped routing, middleware guards and access logging
Sources
Also known as GHSA-6765-c87h-8mrf, GO-2026-6204, MINI-j9fm-fh53-7w2f, MINI-pfw6-6q2j-fxq6, MINI-rr56-79fm-7x6w.