Traefik: SNICheck ignores wildcard TLSOptions mappings, allowing domain-fronted mTLS bypass (traefik traefik)
At a glance
- Source
- NVD
- EPSS
- EPSS 0.36 % · percentile 29 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- GitHub_M
- NVD status
- Modified
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.
Weaknesses (CWE)
- CWE-288 — Authentication Bypass Using an Alternate Path or Channel
- CWE-807 — Reliance on Untrusted Inputs in a Security Decision
References
- https://github.com/traefik/traefik/security/advisories/GHSA-5r4w-85f3-pw66
- https://github.com/traefik/traefik/releases/tag/v3.7.3
- https://access.redhat.com/security/cve/CVE-2026-48491
- https://bugzilla.redhat.com/show_bug.cgi?id=2491923
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-48491.json
- https://access.redhat.com/errata/RHSA-2026:62260
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 4.0 | HIGH 7.8 | 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 | GitHub_M |
| CVSS 3.1 | CRITICAL 9.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N | redhat-SADP |
| CVSS 4.0 | HIGH 7.8 | 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 | NVD · security-advisories@github.com (Secondary) |
| CVSS 3.1 | CRITICAL 10.0 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N | NVD · nvd@nist.gov (Primary) |
| CVSS 3.1 | CRITICAL 9.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N | NVD · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c (Secondary) |
Advisories
- GHSA-5r4w-85f3-pw66 — Traefik: SNICheck ignores wildcard TLSOptions mappings, allowing domain-fronted mTLS bypass
- GO-2026-5152 — Traefik: SNICheck ignores wildcard TLSOptions mappings in github.com/traefik/traefik
European references
- ENISA EUVD · EUVD-2026-38575
- GCVE · GCVE-0-2026-48491
CERT-FR advisories
- CERTFR-2026-AVI-0690 — Multiples vulnérabilités dans Traefik · cert.ssi.gouv.fr
Affected configurations (NVD CPE)
cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*≥ 3.7.0 < 3.7.3
Affected products
| Product | Versions |
|---|---|
| traefik · traefik | affected >= 3.7.0, < 3.7.3 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |