CVE-2026-88010 Traefik: BasicAuth singleflight coalescing reintroduces an unauthenticated username-enumeration timing oracle
An attacker can enumerate valid usernames in Traefik BasicAuth configurations by exploiting timing differences caused by singleflight coalescing.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-88010?
CVE-2026-88010 is a medium-severity vulnerability in Traefik Traefik, published on 22 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Traefik is an open source HTTP reverse proxy and load balancer. From 3.6.11 until 3.7.13, 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.
Weakness: CWE-208
Which versions are affected by CVE-2026-88010?
3 open source packages ship an affected version, including Traefik and github.com/traefik/traefik. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
Traefik Go | From 3.6.11 | 3.7.13 |
Traefik Go | From 3.6.11 | 3.7.13 |
github.com/traefik/traefik Go | All versions | None |
Products include Traefik Traefik.
How do I fix CVE-2026-88010?
Upgrade Traefik to 3.7.13 or later.
Is CVE-2026-88010 being exploited?
There is no known exploitation of CVE-2026-88010 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-8fcf-v89g-xpg6, GO-2026-6558, MINI-c7x8-8cwp-h837, MINI-pw97-66qj-pmq6.