{"cve":"CVE-2025-66491","nvd":{"published":"2025-12-09T01:16:55.720","modified":"2026-10-14T22:10:00.210","status":"Analyzed","description":"Traefik is an HTTP reverse proxy and load balancer. Versions 3.5.0 through 3.6.2 have inverted TLS verification logic in the nginx.ingress.kubernetes.io/proxy-ssl-verify annotation. Setting the annotation to \"on\" (intending to enable backend TLS certificate verification) actually disables verification, allowing man-in-the-middle attacks against HTTPS backends when operators believe they are protected. This issue is fixed in version 3.6.3.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N","score":5.9},"cwes":["CWE-295"],"references":["https://github.com/traefik/traefik/commit/14a1aedf5704673d875d210d7bacf103a43c77e4","https://github.com/traefik/traefik/releases/tag/v3.6.3","https://github.com/traefik/traefik/security/advisories/GHSA-7vww-mvcr-x6vj"],"products":["traefik:traefik"],"source":"nvd","synced_at":"2026-10-19T22:16:40.427100871+00:00"},"epss":{"cve":"CVE-2025-66491","score":0.00221,"percentile":0.12518,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-7vww-mvcr-x6vj","url":"https://osv.dev/vulnerability/GHSA-7vww-mvcr-x6vj","summary":"Traefik Inverted TLS Verification Logic in ingress-nginx Provider","modified":"2026-09-10T03:50:31.689588670Z","packages":[{"ecosystem":"Go","name":"github.com/traefik/traefik/v3","purl":"pkg:golang/github.com/traefik/traefik/v3","ranges":[">=3.5.0 <3.6.3"],"fixed":["3.6.3"]}]},{"id":"GO-2025-4205","url":"https://osv.dev/vulnerability/GO-2025-4205","summary":"Traefik Inverted TLS Verification Logic in ingress-nginx Provider in github.com/traefik/traefik","modified":"2026-07-02T14:44:24.399738422Z","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":["all versions"],"fixed":[]},{"ecosystem":"Go","name":"github.com/traefik/traefik/v3","purl":"pkg:golang/github.com/traefik/traefik/v3","ranges":[">=3.5.0 <3.6.3"],"fixed":["3.6.3"]}]}],"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."]}