CVE-2026-26062: 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
Credits
We thank @fuzzztf for responsibly reporting this issue.
Other sources
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.
— MITRE
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-26062?
CVE-2026-26062 has been classified as a denial-of-service (DoS) vulnerability.
How do I fix CVE-2026-26062?
To fix CVE-2026-26062, update the Fleet software to version 4.81.0 or later.
What causes CVE-2026-26062?
CVE-2026-26062 is caused by improper handling of unexpected input values in the gRPC Launcher `PublishLogs` endpoint.
What software versions are affected by CVE-2026-26062?
CVE-2026-26062 affects any version of Fleet prior to 4.81.0.
What impact does CVE-2026-26062 have on systems?
CVE-2026-26062 can cause the Fleet server process to terminate when processing authenticated requests.