CVEvulnerability

CVE-2026-48491

7.8 HIGH Published 2026-06-23 Modified 2026-09-02 Official page ↗
Status
Modified
Published
2026-06-23
Last modified
2026-09-02
Assigner
[email protected]
CVSS 4.0 ([email protected])
7.8 HIGH — 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1 ([email protected])
10.0 CRITICAL — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N
CVSS 3.1 (0b0ca135-0b70-47e7-9f44-1890c2a1c46c)
9.1 CRITICAL — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weaknesses
CWE-288, CWE-807

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.

Affected configurations

• traefik traefik (>= 3.7.0 < 3.7.3)

Related

Weakness · CWE (2)

  • CWE-288 Authentication Bypass Using an Alternate Path or Channel weakness
  • CWE-807 Reliance on Untrusted Inputs in a Security Decision weakness

References