Traefik mTLS bypass via fragmented ClientHello SNI extraction failure
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Fix
- Fixed in 2.11.41, 3.6.11, 3.7.0-ea.2
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: none
- Automatable: yes
- Technical impact: partial
Summary
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.
Timeline
- CVE published
- CISA SSVC assessment
Exploitation: none · Automatable: yes · Technical impact: partial
- Record last updated
Affected versions
- traefik traefik
fixed in 2.11.41; From 3.0.0-beta1 · fixed in 3.6.11; From 3.7.0-ea.1 · fixed in 3.7.0-ea.2
- github.com/traefik/traefikGo
All versions
- github.com/traefik/traefik/v2Go
fixed in 2.11.41
- github.com/traefik/traefik/v3Go
fixed in 3.6.11; From 3.7.0-ea.1 · fixed in 3.7.0-ea.2
- github.com/traefik/traefik/v3Go
From 3.7.0-ea.1 · fixed in 3.7.0-ea.2
- github.com/traefik/traefik/v3Go
fixed in 3.6.11
- github.com/traefik/traefikGo
through 1.7.34