Username enumeration via empty fallback secret
Published Apr 30, 2026 · Updated Apr 30, 2026
Observable timing discrepancy in Traefik Proxy before 2.11.43, 3.6.14, and 3.7.0-rc.2 allows remote attackers to enumerate usernames. The basic_auth.go fallback derives notFoundSecret by using a stored hash as a username key, producing an empty secret that bypasses the intended bcrypt workload. An unauthenticated network client must reach a route using BasicAuth and collect repeated response timings; the bounded consequence is disclosure of which tested usernames exist.
Summary
What happened
Observable timing discrepancy in Traefik Proxy before 2.11.43, 3.6.14, and 3.7.0-rc.2 allows remote attackers to enumerate usernames. The basic_auth.go fallback derives notFoundSecret by using a stored hash as a username key, producing an empty secret that bypasses the intended bcrypt workload. An unauthenticated network client must reach a route using BasicAuth and collect repeated response timings; the bounded consequence is disclosure of which tested usernames exist.
The record
- CVE
- CVE-2026-41263
- Published
- Apr 30, 2026
- Updated
- Apr 30, 2026
- Vendor
- Traefik Labs
- Product
- Traefik Proxy
- Classifications
- CWE-208, T1087
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 30, 2026CVE publishedPublication date reported by the CVE source.
- Apr 30, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 2.11.43
- Affected versionversion=>= 3.0.0-beta1, < 3.6.14
- Affected versionversion=>= 3.7.0-ea.1, < 3.7.0-rc.2
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
- BasicAuth black-box Python timing oracleproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo