Nest: Remote process termination via a deeply nested microservice message pattern

| Field | Value | | --- | --- | | Ecosystem | npm | | Package | `@nestjs/microservices` | | Affected versions | `>= 12.0.0, < 12.0.2` and `< 11.2.4` | | Patched versions | `12.0.2` and `11.2.4` (upgrade to `12.0.3` / `11.2.5`) | ### Summary A single message whose `pattern` is a deeply nested object terminates a NestJS microservice that uses the TCP or RabbitMQ transport. The server serialized the client-supplied pattern with `JSON.stringify` to derive the handler lookup key; on deeply nested input this throws `RangeError: Maximum call stack size exceeded`. The exception escaped the asynchronous message handler as an unhandled promise rejection, which terminates the Node.js process under the default `--unhandled-rejections=throw`. ### Impact Denial of service, one message per crash, repeatable. The attacker needs to be able to reach the transport: connect to the TCP transport's port, or publish to the queue or exchange the service consumes from. The TCP transport performs no authentication by default, so on a reachable port this requires nothing else. Only the **TCP** and **RabbitMQ** transports are affected. The other transports take the pattern as a string from the broker topic or channel and never serialize a client-supplied object to build it. ### Details In `ServerTCP#handleMessage` and `ServerRMQ#handleMessage` the pattern was stringified without a guard: ```ts const pattern = isString(packet.pattern) ? packet.pattern : JSON.stringify(packet.pattern); ``` `JSON.parse` ac