What’s Vulnerable › Vulnerabilities

CVE-2026-32305: Traefik mTLS bypass via fragmented ClientHello SNI extraction failure

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-03-20 · updated 2026-07-15
• Weakness: CWE-287

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.

Affected products

• Traefik: before 2.11.41; from 3.0.0 through 3.6.11; 3.7.0-ea1 — fixed in 2.11.41

How to fix

Upgrade to a fixed version: Traefik 2.11.41. Check the vendor advisory for mitigations.

References

• https://github.com/traefik/traefik/releases/tag/v2.11.41
• https://github.com/traefik/traefik/releases/tag/v3.6.11
• https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.2
• https://github.com/traefik/traefik/security/advisories/GHSA-wvvq-wgcr-9q48
• https://access.redhat.com/errata/RHSA-2026:10175
• https://access.redhat.com/errata/RHSA-2026:21772
• https://access.redhat.com/security/cve/CVE-2026-32305
• https://bugzilla.redhat.com/show_bug.cgi?id=2449595
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-32305.json

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