CVE-2026-48491 Traefik: SNICheck ignores wildcard TLSOptions mappings, allowing domain-fronted mTLS bypass
Attackers can bypass mutual TLS authentication on wildcard routers by exploiting SNICheck's failure to apply wildcard TLS options, accessing protected backends without client certificates.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-48491?
CVE-2026-48491 is a high-severity authentication bypass vulnerability in Traefik Traefik, published on 23 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-48491?
6 open source packages ship an affected version, including github.com/traefik/traefik/v2 and github.com/traefik/traefik/v3. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/traefik/traefik/v2 Go | All versions | 2.11.48 |
github.com/traefik/traefik/v2 Go | All versions | 2.11.48 |
github.com/traefik/traefik/v2 Go | All versions | 2.11.48 |
github.com/traefik/traefik/v3 Go | From 3.7.0 | 3.7.3 |
github.com/traefik/traefik/v3 Go | From 3.7.0 | 3.7.3 |
github.com/traefik/traefik/v3 Go | From 3.7.0 | 3.7.3 |
Products include Traefik Traefik.
How do I fix CVE-2026-48491?
Upgrade github.com/traefik/traefik/v2 to 2.11.48 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-48491 being exploited?
There is no known exploitation of CVE-2026-48491 in the wild and no public exploit code.
Other vulnerabilities in Traefik Traefik
- CVE-2024-45410 HTTP client can remove the X-Forwarded headers in Traefik
- CVE-2026-88877 Traefik v3.7.0 Authentication Bypass via from-to-www-redirect
- CVE-2026-85595 Traefik before v2.11.55 and v3.0.0 through v3.7.10 Authentication Bypass via digestAuth
- CVE-2026-88007 Traefik HTTP/3 Backend NTLM Connection Reuse
- CVE-2026-88009 Traefik: Rootless HTTP/1 request-target routes as "/" but is forwarded verbatim, bypassing path-scoped routing, middleware guards and access logging
Sources
Also known as GHSA-5r4w-85f3-pw66, GO-2026-5152, MINI-35hp-9r2c-55gh, MINI-vm74-x7qx-v6q6, MINI-vpwx-gc9h-93c9.