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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-88010
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-22 16:18:06 UTC
Updated2026-09-24 21:22:19 UTC
DescriptionTraefik 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.

Risk And Classification

Primary CVSS: v4.0 6.3 MEDIUM from [email protected]

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS: 0.006910000 probability, percentile 0.507900000 (date 2026-09-25)

Problem Types: CWE-208 | CWE-208 CWE-208: Observable Timing Discrepancy

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary6.3MEDIUMCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/C...
4.0CNADECLARED6.3MEDIUMCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
Present
Privileges Required
None
User Interaction
None
Confidentiality
Low
Integrity
None
Availability
None
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Traefik Traefik affected >= 3.6.11, < 3.7.13 Not specified

References

ReferenceSourceLinkTags
github.com/traefik/traefik/releases/tag/v3.7.13 [email protected] github.com
github.com/traefik/traefik/commit/ddc1bf4660b85fd61fafdd821eb8216fb1a0b130 [email protected] github.com
github.com/traefik/traefik/security/advisories/GHSA-8fcf-v89g-xpg6 [email protected] github.com
github.com/traefik/traefik/pull/13816 [email protected] github.com
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