CVE-2026-32305 Traefik mTLS bypass via fragmented ClientHello SNI extraction failure
Attackers can bypass mutual TLS authentication in Traefik by sending fragmented ClientHello packets, accessing protected services without valid 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-2026-32305?
CVE-2026-32305 is a high-severity authentication bypass vulnerability in Traefik Traefik, published on 20 Mar 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. Versions 2.11.40 and below, 3.0.0-beta1 through 3.6.11, and 3.7.0-ea.1 are vulnerable to mTLS bypass through the TLS SNI pre-sniffing logic related to fragmented ClientHello packets. When a TLS ClientHello is fragmented across multiple records, Traefik's SNI extraction may fail with an EOF and return an empty SNI. The TCP router then falls back to the default TLS configuration, which does not require client certificates by default. This allows an attacker to bypass route-level mTLS enforcement and access services that should require mutual TLS authentication. This issue is patched in versions 2.11.41, 3.6.11 and 3.7.0-ea.2.
Which versions are affected by CVE-2026-32305?
11 open source packages ship an affected version, including github.com/traefik/traefik/v3, github.com/traefik/traefik and github.com/traefik/traefik/v2. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/traefik/traefik/v3 Go | All versions | 3.6.11, 3.7.0-ea.2 |
github.com/traefik/traefik/v3 Go | All versions | 3.6.11 |
github.com/traefik/traefik/v3 Go | All versions | 3.6.11 |
github.com/traefik/traefik/v3 Go | From 3.7.0-ea.1 | 3.7.0-ea.2 |
github.com/traefik/traefik/v3 Go | From 3.7.0-ea.1 | 3.7.0-ea.2 |
github.com/traefik/traefik Go | All versions | None |
5 more packages
github.com/traefik/traefik Go | All versions to 1.7.34 | None |
github.com/traefik/traefik Go | All versions to 1.7.34 | None |
github.com/traefik/traefik/v2 Go | All versions | 2.11.41 |
github.com/traefik/traefik/v2 Go | All versions | 2.11.41 |
github.com/traefik/traefik/v2 Go | All versions | 2.11.41 |
Products include Traefik Traefik.
How do I fix CVE-2026-32305?
Upgrade github.com/traefik/traefik/v3 to a fixed version for your release line: 3.6.11 or 3.7.0-ea.2.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-32305 being exploited?
There is no known exploitation of CVE-2026-32305 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 CLEANSTART-2026-SJ19949, GHSA-wvvq-wgcr-9q48, GO-2026-4793, MINI-3h24-53p3-6r9f, MINI-h563-q5ch-pwc4, MINI-vh5g-pvf6-hq8x.