Traefik is an HTTP reverse proxy and load balancer. Prior to versions 3.6.11 and 3.7.0-ea.2, Traefik's Knative provider builds router rules by interpolating user-controlled values into backtick-delimited rule expressions without escaping. In live cluster validation, Knative `rules[].hosts[]` was exploitable for host restriction bypass (for example `tenant.example.com`) || Host(`attacker.com`), producing a router that serves attacker-controlled hosts. Knative `headers[].exact` also allows rule-syntax injection and proves unsafe rule construction. In multi-tenant clusters, this can route unauthorized traffic to victim services and lead to cross-tenant traffic exposure. Versions 3.6.11 and 3.7.0-ea.2 patch the issue.
https://github.com/traefik/traefik/security/advisories/GHSA-67jx-r9pv-98rj
Published: 2026-03-27
Updated: 2026-04-03
Base Score: 6.8
Vector: CVSS2#AV:N/AC:L/Au:S/C:C/I:N/A:N
Severity: Medium
Base Score: 7.7
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
Severity: High
Base Score: 6.3
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:N/SA:N
Severity: Medium
EPSS: 0.00015