Medium 6.3Published Sep 22, 2026

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

Updated under an hour ago (2026-10-19 08:00 UTC)

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No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

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.

CVSS: 6.3 MEDIUM (v4.0, CNA)CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
Weakness (CWE): CWE-208
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Awaiting Analysis
Record last updated: Sep 22, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

traefik traefik traefik:traefik (from the name)	from 3.6.11, < 3.7.13	CNA record

References

https://github.com/traefik/traefik/security/advisories/GHSA-8fcf-v89g-xpg6x-refsource-confirm
https://github.com/traefik/traefik/pull/13816x-refsource-misc
https://github.com/traefik/traefik/commit/ddc1bf4660b85fd61fafdd821eb8216fb1a0b130x-refsource-misc
https://github.com/traefik/traefik/releases/tag/v3.7.13x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.