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TI-2026-35853 Aliases CVE-2026-48491GHSA-5r4w-85f3-pw66

Traefik: SNICheck ignores wildcard TLSOptions mappings, allowing domain-fronted mTLS bypass

Priority MEDIUM 42CWE-288Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Security bypass
Confidentiality · integrity · availability
None · None · None
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-288.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00357 29th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed traefik (traefik): 3.7.3github.com/traefik/traefik/v2 (Go): 2.11.48+1 more productRed Hat: 1 advisory

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
traefiktraefik3.7.0 to before 3.7.33.7.3Patch availableCNA
—github.com/traefik/traefik/v2 (Go)before 2.11.482.11.48Patch availableGHSA-5r4w-85f3-pw66
—github.com/traefik/traefik/v3 (Go)3.7.0 to before 3.7.33.7.3Patch availableGHSA-5r4w-85f3-pw66
  • traefik Vendortraefik Affected 3.7.0 to before 3.7.3 Fixed in 3.7.3 Patch available CNA
  • github.com/traefik/traefik/v2 (Go) Vendor— Affected before 2.11.48 Fixed in 2.11.48 Patch available GHSA-5r4w-85f3-pw66
  • github.com/traefik/traefik/v3 (Go) Vendor— Affected 3.7.0 to before 3.7.3 Fixed in 3.7.3 Patch available GHSA-5r4w-85f3-pw66

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*3.7.0 to before 3.7.3Vulnerabletraefik
  • cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:* Versions 3.7.0 to before 3.7.3 Vulnerable ·traefik

Remediation

  • Fix · CNA traefik (traefik) Fixed in 3.7.3
  • Fix · GHSA-5r4w-85f3-pw66 github.com/traefik/traefik/v2 (Go) Fixed in 2.11.48 Advisory →
  • Fix · GHSA-5r4w-85f3-pw66 github.com/traefik/traefik/v3 (Go) Fixed in 3.7.3 Advisory →

Red Hat 1 advisory

  • RHSA-2026:62260 Released 2026-09-01 · Red Hat rating Important
    Red Hat OpenShift Dev Spaces 3.30.0 Release.
    • Red Hat OpenShift Dev Spaces 3.30 registry.redhat.io/devspaces/code-rhel9, registry.redhat.io/devspaces/configbump-rhel9, registry.redhat.io/devspaces/dashboard-rhel9 +7

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat OpenShift Dev Spaces 3.30Fixed RHSA-2026:62260
Not affected: 1 product
  • Red Hat OpenShift Dev Spaces 3.30

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-48491
  2. 2026-10-03 Alias added: GHSA-5r4w-85f3-pw66

References

Exploit 1

Patch 1

Advisory 1

Other 7

  • TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
  • TI-2023-25774 Uncontrolled Resource Consumption in Traefik CVSS 3.1HIGH 7.5
  • TI-2025-40914 Traefik doesn't Prevent Path Normalization Bypass in Router + Middleware Rules CVSS 4.0MEDIUM 6.9
  • TI-2022-07529 Authorization header displayed in the debug logs CVSS 3.1MEDIUM 6.5
  • TI-2024-30459 HTTP client can remove the X-Forwarded headers in Traefik CVSS 3.1CRITICAL 9.8
  • TI-2026-60261 Traefik v3.7.0 Authentication Bypass via from-to-www-redirect CVSS 4.0CRITICAL 9.3
See all 83 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences