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.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
None
No disruption
CVSS Vector v4.0
Weakness Type (CWE)
Vulnerable Products 3
| Configuration | From (including) | Up to (excluding) |
|---|---|---|
|
Traefik Traefik
cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*
|
— |
2.11.41
|
|
Traefik Traefik
cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*
|
3.0.0
|
<= 3.6.11
|
|
Traefik Traefik
cpe:2.3:a:traefik:traefik:3.7.0:ea1:*:*:*:*:*:*
|
— | — |
References 4
https://github.com/traefik/traefik/releases/tag/v2.11.41
security-advisories@github.com
https://github.com/traefik/traefik/releases/tag/v3.6.11
security-advisories@github.com
https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.2
security-advisories@github.com
https://github.com/traefik/traefik/security/advisories/GHSA-wvvq-wgcr-9q48
security-advisories@github.com