Unauthenticated Remote Shutdown in TypeSpec Spector

The @typespec/spector mock server, a component of the TypeSpec ecosystem, contains a critical security flaw (CWE-306) allowing for unauthenticated remote denial-of-service. An Express-based admin route registered at POST /.admin/stop is exposed without any authentication, authorization tokens, Origin header verification, or IP-based source restrictions. By default, the server binds to 0.0.0.0, rendering the endpoint accessible to any client with network connectivity to the service port, rather than restricting it to localhost.

When triggered, the handler logs an exit signal and executes process.exit(0), effectively shutting down the mock server process. This vulnerability is particularly impactful for CI/CD pipelines, shared cloud developer environments, and containerized deployments where the service port is reachable from external or less-trusted network segments. No credentials are required to successfully invoke the shutdown signal.

Attack Chain

1. The target server is initiated using tsp-spector serve, causing it to bind to 0.0.0.0:3000 by default.
2. The application registers the internalRouter which includes the unauthenticated administrative route at /.admin/stop.
3. An attacker identifies the mock server port (default 3000) through network scanning or organizational knowledge.
4. The attacker sends a crafted POST request to http://<target-host>:3000/.admin/stop with no headers or credentials.
5. The application’s Express router accepts the unauthenticated request as a legitimate admin command.
6. The backend handler executes process.exit(0), terminating the Node.js process.
7. The mock server ceases all operations, resulting in a successful denial-of-service against the testing environment.

Impact

Successful exploitation results in an immediate, unauthenticated denial-of-service. Because the service is used in CI/CD and developer testing pipelines, a successful attack can halt integration testing, break automated deployment flows, and cause downstream disruption in development workflows. Given the lack of default access controls and the broad network binding, this vulnerability poses a high risk to any organization running Spector in shared network environments.

Recommendation

Prioritize the immediate upgrade of all @typespec/spector instances to version 0.1.0-alpha.27 or later, which incorporates mandatory authentication or restricted access patterns. In environments where an immediate upgrade is not possible, implement firewall rules to restrict access to port 3000 solely to local loopback addresses or trusted management IP ranges. Monitor web server logs for HTTP POST requests to the /.admin/stop endpoint and alert on unauthorized access attempts.

Impact

• CWE-306: Missing Authentication for Critical Function
• CVSS 7.5 (High)