Fleet server may terminate unexpectedly when handling certain gRPC requests

### Summary Fleet contained a denial-of-service (DoS) issue in the gRPC Launcher `PublishLogs` endpoint. In affected versions, certain unexpected input values were not handled gracefully, which could cause the Fleet server process to terminate while processing an authenticated request from an enrolled Launcher host. ### Impact An authenticated attacker with access to any enrolled Launcher node key could cause an immediate and complete denial of service by sending a single gRPC request to the `PublishLogs` endpoint. This vulnerability impacts **availability only**. There is: - No exposure of sensitive data - No authentication bypass - No privilege escalation - No integrity impact ### Workarounds If upgrading immediately is not possible, the following mitigations can reduce exposure: - Restrict network access to the Fleet gRPC endpoint where feasible (for example, limiting inbound access to known host IP ranges). - Deploy Fleet behind infrastructure that terminates or filters gRPC traffic if Launcher log ingestion is not required. - Monitor for repeated Fleet process crashes or unexpected restarts indicating potential exploitation. ### For More Information If you have any questions or concerns about this advisory, please contact us at: Email us at [security@fleetdm.com](mailto:security@fleetdm.com) ### Credits We thank @fuzzztf for responsibly reporting this issue.