CVE-2026-48491
Published: 23 June 2026
Summary
CVE-2026-48491 is a high-severity Authentication Bypass Using an Alternate Path or Channel (CWE-288) vulnerability in Traefik Traefik. Its CVSS base score is 7.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 15.7th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-38575
Vulnerability details
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Bypass of mTLS client cert validation on public-facing reverse proxy directly enables exploitation of the exposed application to reach protected resources without authentication.
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Authorizing remote access reduces the ability to bypass authentication via unauthorized alternate remote channels.
Users can identify logons via alternate paths or channels by reviewing the previous logon time.
Adaptive requirements can apply across access paths, reducing the ability to bypass authentication via alternate channels or paths.
Centralized IdPs close alternate authentication paths that enable bypass.
Enforces authentication for non-organizational users, making it harder to bypass via alternate paths or channels.
Prevents reliance on untrusted matching results for security-relevant decisions by enforcing verification and contest procedures.
Requires authentication to occur exclusively over the isolated trusted path, directly preventing bypass via alternate or untrusted channels.
Providing authoritative attributes with the data reduces the need for security decisions to rely on untrusted external inputs.