Vulnerability · Published Mar 20, 2026 · Assigned by GitHub_M
CVE-2026-32305Traefik mTLS bypass via fragmented ClientHello SNI extraction failure
High 8.3
In plain English
A high-severity improper authentication in traefik from traefik. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 37% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/traefik/traefik | no fix listed | GHSA-wvvq-wgcr-9q48 |
| Go | github.com/traefik/traefik | no fix listed | GO-2026-4793 |
| Go | github.com/traefik/traefik/v2 | 2.11.41 | GHSA-wvvq-wgcr-9q48 |
| Go | github.com/traefik/traefik/v2 | 2.11.41 | GO-2026-4793 |
| Go | github.com/traefik/traefik/v3 | 3.7.0-ea.2 | GHSA-wvvq-wgcr-9q48 |
| Go | github.com/traefik/traefik/v3 | 3.6.11, 3.7.0-ea.2 | GO-2026-4793 |
| Go | github.com/traefik/traefik/v3 | 3.6.11 | GHSA-wvvq-wgcr-9q48 |
Affected products (as reported)
Weakness: CWE-287, CWE-1188, CWE-179 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L
References
- https://github.com/traefik/traefik/security/advisories/GHSA-wvvq-wgcr-9q48 x_refsource_CONFIRM
- https://github.com/traefik/traefik/releases/tag/v2.11.41 x_refsource_MISC
- https://github.com/traefik/traefik/releases/tag/v3.6.11 x_refsource_MISC
- https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.2 x_refsource_MISC
- https://access.redhat.com/security/cve/CVE-2026-32305 vdb-entry, x_refsource_REDHAT
- RHBZ#2449595 issue-tracking, x_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-32305.json x_sadp-csaf-vex
- https://access.redhat.com/errata/RHSA-2026:10175 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:21772 vendor-advisory, x_refsource_REDHAT