{"cve":"CVE-2026-41263","nvd":{"published":"2026-04-30T21:16:33.390","modified":"2026-06-17T10:46:24.157","status":"Analyzed","description":"Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.43, 3.6.14, and 3.7.0-rc.2, there is a timing side-channel vulnerability in Traefik's BasicAuth middleware that allows an attacker to enumerate valid usernames through response-time differences. The variable intended to hold a constant-time fallback secret always resolves to an empty string, causing the constant-time comparison to short-circuit in microseconds rather than performing a full bcrypt evaluation. This restores the original timing oracle and makes it possible to distinguish existing users from non-existing ones by measuring authentication response times. This issue has been patched in versions 2.11.43, 3.6.14, and 3.7.0-rc.2.","cvss_v4":{"vector":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N","score":6.3},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N","score":3.7},"cwes":["CWE-208"],"references":["https://github.com/traefik/traefik/releases/tag/v2.11.43","https://github.com/traefik/traefik/releases/tag/v3.6.14","https://github.com/traefik/traefik/releases/tag/v3.7.0-rc.2","https://github.com/traefik/traefik/security/advisories/GHSA-6x2q-h3cr-8j2h"],"products":["traefik:traefik"],"source":"nvd","synced_at":"2026-10-19T22:33:09.003606135+00:00"},"epss":{"cve":"CVE-2026-41263","score":0.00369,"percentile":0.30795,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-6x2q-h3cr-8j2h","url":"https://osv.dev/vulnerability/GHSA-6x2q-h3cr-8j2h","summary":"Traefik: A timing side-channel vulnerability allows for valid username enumeration via BasicAuth middleware","modified":"2026-06-25T19:56:38.840221951Z","packages":[{"ecosystem":"Go","name":"github.com/traefik/traefik/v3","purl":"pkg:golang/github.com/traefik/traefik/v3","ranges":[">=3.7.0-ea.1 <3.7.0-rc.2"],"fixed":["3.7.0-rc.2"]},{"ecosystem":"Go","name":"github.com/traefik/traefik/v3","purl":"pkg:golang/github.com/traefik/traefik/v3","ranges":[">=3.0.0-beta1 <3.6.14"],"fixed":["3.6.14"]},{"ecosystem":"Go","name":"github.com/traefik/traefik/v2","purl":"pkg:golang/github.com/traefik/traefik/v2","ranges":["<2.11.43"],"fixed":["2.11.43"]},{"ecosystem":"Go","name":"github.com/traefik/traefik","purl":"pkg:golang/github.com/traefik/traefik","ranges":["<=1.7.34"],"fixed":[]}]},{"id":"GO-2026-5195","url":"https://osv.dev/vulnerability/GO-2026-5195","summary":"Traefik: A timing side-channel vulnerability allows for valid username enumeration via BasicAuth middleware in github.com/traefik/traefik","modified":"2026-06-25T19:45:13.812817129Z","packages":[{"ecosystem":"Go","name":"github.com/traefik/traefik","purl":"pkg:golang/github.com/traefik/traefik","ranges":["all versions"],"fixed":[]},{"ecosystem":"Go","name":"github.com/traefik/traefik/v2","purl":"pkg:golang/github.com/traefik/traefik/v2","ranges":["<2.11.43"],"fixed":["2.11.43"]},{"ecosystem":"Go","name":"github.com/traefik/traefik/v3","purl":"pkg:golang/github.com/traefik/traefik/v3","ranges":[">=3.0.0-beta1 <3.6.14",">=3.7.0-ea.1 <3.7.0-rc.2"],"fixed":["3.6.14","3.7.0-rc.2"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}