Fleet is open source device management software. Prior to version 4.81.0, 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. 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, and no integrity impact. Version 4.81.0 contains a patch. 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; and/or monitor for repeated Fleet process crashes or unexpected restarts indicating potential exploitation.

Affected: Go: github.com/fleetdm/fleet/v4

### 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.

Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in Fleet ausnutzen, um Sicherheitsmaßnahmen zu umgehen, Daten zu manipulieren oder offenzulegen oder einen Denial-of-Service-Zustand herbeizuführen.