CVE-2026-63121: Kubewarden trusted-repos-policy: uppercase registry host bypasses registry/image deny rules

Vulnerability summary

CVE-2026-63121 is a medium (CVSS 6.3) Improper Handling of Case Sensitivity vulnerability in kubewarden policies. EPSS estimates a 0.19% chance of exploitation in the next 30 days, higher than 9% of scored vulnerabilities.

Timeline

1. 30-10-2026
   PublishedVulnerability first disclosed.

Description

Kubewarden policies is a collection of WebAssembly policies for securing and governing Kubernetes clusters. For versions provisionally classified as affected before 2.1.2, `trusted-repos-policy` compares an image's `registry` hostname against `reject lists` and `allow lists` case-sensitively even though `registry` DNS names are case-insensitive. An image with an uppercase or mixed-case `registry` hostname can miss a rejection rule for the equivalent lowercase host, so the admission policy accepts a resource whose container runtime pulls the same prohibited image. Only reject-list configurations have this bypass: allow-list configurations fail closed by over-denying differently cased hostnames. The security consequences depend on the configured rejection policy and deployment environment. This issue is fixed in version 2.1.2.

• CWE-178Improper Handling of Case SensitivityThe product does not properly account for differences in case sensitivity when accessing or determining the properties of a resource, leading to inconsistent results.