Summary 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 use…
| CVE ID | CVE-2026-48491 |
| Vendor | go |
| Affected Product | Traefik |
| Vulnerability Type | Vulnerability |
| CVSS Score | 7.5 (HIGH) |
| Actively Exploited | ❌ No known exploitation |
| Patch Status | See Vendor Advisory → |
| Reported By | CYBERDUDEBIVASH SENTINEL APEX Intelligence (via github_advisories) |
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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 notSigma rules, YARA signatures, IOC table, and SIEM queries for Splunk, Elastic, Sentinel, and Chronicle — deployable in 5 minutes.