CVE-2026-61682

Name of the Vulnerable Software and Affected Versions kcp versions prior to 0.31.4 kcp versions prior to 0.32.2

Description The kcp front-proxy fails to remove inbound identity headers before forwarding requests to shards. An authenticated tenant can inject forged headers, which the shard trusts as verified identity assertions. This allows a low-privilege user to escalate privileges to cluster administrator by asserting X-Remote-Group: system:masters, bypassing the authorizer chain across all workspaces on the shard. Additionally, attackers can forge authorization.kcp.io/warrant to assume arbitrary identities or authentication.kcp.io/scopes to escape cluster-scoping. This results in a complete multi-tenant isolation break, enabling arbitrary reading, writing, or deletion of resources, secrets, RBAC data, APIExports, APIBindings, and LogicalClusters.

Technical details include the exploitation of the following headers:

Recommendations Update to version 0.31.4. Update to version 0.32.2. As a temporary mitigation, use an external proxy to strip X-Remote-User, X-Remote-Group, and all X-Remote-Extra-* headers from inbound requests before they reach the kcp front-proxy.