Severity by source
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
Network-reachable and unauthenticated (AV:N/PR:N), but the concurrency timing race makes reliable exploitation high-complexity (AC:H); only username existence leaks, so C:L with no integrity or availability impact.
Primary rating from Vendor (GitHub_M).
CVSS VectorVendor: GitHub_M
Lifecycle Timeline
4DescriptionCVE.org
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.
AnalysisAI
Concurrent HTTP requests to Traefik's BasicAuth middleware can reveal whether a username is configured, because absent usernames are collapsed into a single deduplicated (singleflight) computation while real usernames each trigger a separate password hash - a measurable timing discrepancy that unauthenticated, remote attackers can exploit. Only Traefik 3.6.11 through 3.7.12 are affected, and only when BasicAuth middleware is enabled; Traefik v2 and Digest authentication are explicitly unaffected. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Requires the target Traefik instance (version 3.6.11 through 3.7.12) to have a BasicAuth middleware configured; Traefik v2 and Digest authentication are explicitly not affected. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | This is a genuine but low-severity confidentiality issue, not a high-priority emergency. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Vendor-released patch: Traefik 3.7.13 - upgrade all instances running 3.6.11 through 3.7.12 with BasicAuth middleware configured to v3.7.13 or later (release notes: https://github.com/traefik/traefik/releases/tag/v3.7.13; advisory: https://github.com/traefik/traefik/security/advisories/GHSA-8fcf-v89g-xpg6). … Detailed patch versions, workarounds, and compensating controls in full report. |
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Same weakness CWE-208 – Observable Timing Discrepancy
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External POC / Exploit Code
Leaving vuln.today
EUVD-2026-84532
GHSA-8fcf-v89g-xpg6