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National Vulnerability Database

National Vulnerability Database

NVD

National Vulnerability Database
  1. Vulnerabilities

CVE-2026-48491 Detail

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.


Metrics

 
NVD enrichment efforts reference publicly available information to associate vector strings. CVSS information contributed by other sources is also displayed.
CVSS 4.0 Severity and Vector Strings:

NIST CVSS score
NIST: NVD
N/A
NVD assessment not yet provided.

Nist CVSS score does not match with CNA score
CNA:  GitHub, Inc.
CVSS-B 7.8 HIGH
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

References to Advisories, Solutions, and Tools

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URL Source(s) Tag(s)
https://access.redhat.com/security/cve/CVE-2026-48491 redhat-SADP
https://bugzilla.redhat.com/show_bug.cgi?id=2491923 redhat-SADP
https://github.com/traefik/traefik/releases/tag/v3.7.3 GitHub, Inc. Patch  Release Notes 
https://github.com/traefik/traefik/security/advisories/GHSA-5r4w-85f3-pw66 GitHub, Inc. Exploit  Mailing List  Patch  Vendor Advisory 
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-48491.json redhat-SADP

Weakness Enumeration

CWE-ID CWE Name Source
CWE-288 Authentication Bypass Using an Alternate Path or Channel GitHub, Inc.  
CWE-807 Reliance on Untrusted Inputs in a Security Decision redhat-SADP  

Known Affected Software Configurations Switch to CPE 2.2

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Change History

5 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2026-48491
NVD Published Date:
06/23/2026
NVD Last Modified:
07/14/2026
Source:
GitHub, Inc.