A Denial of Service vulnerability in Fleet's gRPC Launcher endpoint allows an authenticated host to crash the entire Fleet server process by sending an unexpected log type value. The server terminates immediately, disrupting all connected hosts, MDM enrollments, and API consumers.
An attacker with access to a valid Launcher node key can send a specially crafted gRPC request to the Fleet server that triggers an unrecoverable server crash. The gRPC server lacks appropriate error recovery handling, meaning the entire Fleet process terminates rather than gracefully rejecting the malformed input.
Because the crash is instant and repeatable, an attacker could script repeated requests to prevent the server from recovering, resulting in a persistent denial of service until a patched version is deployed.
There is no workaround for this issue other than upgrading to a patched version.
If there are any questions or comments about this advisory:
Send an email to [email protected]
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Fleet thanks @fuzzztf for responsibly reporting this issue.
| Score | Percentile |
|---|---|
| 0.06% | 17.34% |
| Base score | Version | Severity | Vector |
|---|---|---|---|
| 6.6 | 4.0 | — |
|
| Type | Value |
|---|---|
| GHSA | GHSA-w254-4hp5-7cvv ↗ |
| CVE | CVE-2026-34388 ↗ |
| CWE id | Name |
|---|---|
| CWE-703 | Improper Check or Handling of Exceptional Conditions |
Vulnerable version ranges and first patched releases as published by GitHub.
| Ecosystem | Package | Vulnerable range | First patched | Vulnerable functions |
|---|---|---|---|---|
| go | github.com/fleetdm/fleet/v4 | < 4.81.0 | 4.81.0 | — |