CVE-2026-53713

Envoy Gateway contains an input validation flaw (CWE-20) in the Lua validator used for EnvoyExtensionPolicy resources: the to_absolute_normalized_path function in internal/gatewayapi/luavalidator/security.lua fails to collapse redundant path separators (e.g., double slashes) before is_critical_path checks the code under default Strict validation. Because Linux resolves '//etc/...' identically to '/etc/...', an attacker who can submit an EnvoyExtensionPolicy with embedded Lua can open files that the validator was designed to block, reading arbitrary files from the gateway controller pod. Exposed data can include Kubernetes service-account tokens, TLS certificates, and process environment variables, which can then be used to reach the Kubernetes API Server or the Gateway xDS server. Any deployment running Envoy Gateway versions prior to 1.7.4 or 1.8.1 where users beyond the trusted cluster administrators can create EnvoyExtensionPolicies (e.g., multi-tenant clusters) is affected. There is no known public PoC, the issue is not in the CISA KEV catalog, and no exploitation has been reported; fixes are available in versions 1.7.4 and 1.8.1.

What to do: Upgrade Envoy Gateway to 1.7.4 or 1.8.1 as soon as possible. Until then, restrict RBAC so only trusted administrators can create or modify EnvoyExtensionPolicy resources, and audit existing policies for Lua that reads files with redundant path separators. If less-trusted users have applied Lua extensions on an unpatched cluster, rotate the gateway controller's service-account credentials and TLS certificates and review Kubernetes API Server audit logs for anomalous use.