{"cve":"CVE-2026-48491","nvd":{"published":"2026-06-23T20:16:48.123","modified":"2026-09-02T13:17:59.610","status":"Modified","description":"Traefik is an HTTP reverse proxy and load balancer. From 3.7.0 until 3.7.3, there is a high severity vulnerability in Traefik's domain-fronting protection (SNICheck) that allows an unauthenticated client to bypass mutual TLS enforced through wildcard router TLSOptions. When a router uses a wildcard host rule such as Host(*.example.com) with stricter TLS options (for example RequireAndVerifyClientCert), SNICheck resolves the TLS options for the HTTP Host header using exact map lookups only and never applies wildcard matching. If another permissive SNI is served on the same entrypoint, an attacker can complete the TLS handshake under the permissive options and then send an HTTP Host header targeting the wildcard-protected backend, reaching it without presenting a client certificate. This affects the regular HTTPS / HTTP-2 path and does not require HTTP/3. This vulnerability is fixed in 3.7.3.","cvss_v4":{"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N","score":7.8},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N","score":10.0},"cwes":["CWE-288","CWE-807"],"references":["https://github.com/traefik/traefik/releases/tag/v3.7.3","https://github.com/traefik/traefik/security/advisories/GHSA-5r4w-85f3-pw66","https://access.redhat.com/errata/RHSA-2026:62260","https://access.redhat.com/security/cve/CVE-2026-48491","https://bugzilla.redhat.com/show_bug.cgi?id=2491923"],"products":["traefik:traefik"],"source":"nvd","synced_at":"2026-10-19T22:41:17.107060303+00:00"},"epss":{"cve":"CVE-2026-48491","score":0.00357,"percentile":0.29459,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-5r4w-85f3-pw66","url":"https://osv.dev/vulnerability/GHSA-5r4w-85f3-pw66","summary":"Traefik: SNICheck ignores wildcard TLSOptions mappings, allowing domain-fronted mTLS bypass","modified":"2026-09-02T15:45:19.838193649Z","packages":[{"ecosystem":"Go","name":"github.com/traefik/traefik/v2","purl":"pkg:golang/github.com/traefik/traefik/v2","ranges":["<2.11.48"],"fixed":["2.11.48"]},{"ecosystem":"Go","name":"github.com/traefik/traefik/v3","purl":"pkg:golang/github.com/traefik/traefik/v3","ranges":[">=3.7.0 <3.7.3"],"fixed":["3.7.3"]}]},{"id":"GO-2026-5152","url":"https://osv.dev/vulnerability/GO-2026-5152","summary":"Traefik: SNICheck ignores wildcard TLSOptions mappings in github.com/traefik/traefik","modified":"2026-08-11T20:33:01.906417877Z","packages":[{"ecosystem":"Go","name":"github.com/traefik/traefik/v2","purl":"pkg:golang/github.com/traefik/traefik/v2","ranges":["<2.11.48"],"fixed":["2.11.48"]},{"ecosystem":"Go","name":"github.com/traefik/traefik/v3","purl":"pkg:golang/github.com/traefik/traefik/v3","ranges":[">=3.7.0 <3.7.3"],"fixed":["3.7.3"]}]}],"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."]}