Mutual TLS Bypass in Traefik's Reverse Proxy for HTTP and Load Balancer
CVE-2026-48491

7.8HIGH

Key Information:

Vendor

Traefik

Status
Traefik
Vendor
CVE Published:
23 June 2026

What is CVE-2026-48491?

A vulnerability in Traefik's domain-fronting protection (SNICheck) allows unauthenticated clients to bypass mutual TLS when using wildcard router TLSOptions from versions 3.7.0 to 3.7.3. This occurs when routers with wildcard host rules, such as Host(*.example.com), have stricter TLS options enforced. SNICheck fails to apply wildcard matching during the TLS handshake and only validates against exact mappings, permitting an attacker to interact with the protected backend without a valid client certificate. This risk affects both HTTPS and HTTP/2 connections and does not require the use of HTTP/3. Traefik resolved this issue in version 3.7.3.

Affected Version(s)

traefik >= 3.7.0, < 3.7.3

References

https://github.com/traefik/traefik/security/advisories/GH...
x_refsource_CONFIRM
https://github.com/traefik/traefik/releases/tag/v3.7.3
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CVSS V4

Score:
7.8
Severity:
HIGH
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.