CVE-2026-101045: Fleet Homebrew Cask OS Command Injection via Metadata
Fleet-maintained app install and uninstall scripts for macOS are generated from Homebrew cask metadata. In manifests generated before 2026-08-19, the script generator escaped this metadata at some interpolation sites but not all of them, so cask metadata containing shell metacharacters (for example $(...) command substitution) could be carried into scripts that execute as root on managed macOS hosts. An attacker who could land crafted metadata in an upstream Homebrew cask — without needing any Fleet credentials — could achieve arbitrary command execution as root on managed macOS hosts that install or uninstall the affected Fleet-maintained app; exploitation required the crafted metadata to pass both upstream Homebrew cask review and Fleet's review of the automated ingestion pull request. The fix (fleetdm/fleet#51324) landed in Fleet's ingestion pipeline on 2026-08-19 so that all manifests generated on or after that date escape cask metadata at every interpolation site; because manifests are generated centrally and distributed as pre-built content, remediation applied to all deployments with no customer action, and the code fix is included in Fleet v4.92.0.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Fleetto a version that resolves this vulnerability.Fixed in 4.92.0Patch fleetdm/fleet#51324
Event History
Frequently Asked Questions
Which managed hosts were exposed?
Only managed macOS hosts that install or uninstall an affected Fleet-maintained app using a manifest generated before 2026-08-19 were exposed. The vulnerable scripts execute with root privileges.
What would an attacker need to exploit this issue?
An attacker would need to get crafted shell metacharacters into upstream Homebrew cask metadata. The malicious cask metadata would have to pass both upstream Homebrew cask review and Fleet's review of the automated ingestion pull request; no Fleet credentials were required.
Is customer action required to remediate affected manifests?
No. Manifests are generated centrally and distributed as pre-built content, and manifests generated on or after 2026-08-19 escape metadata at all interpolation sites. The code fix is also included in Fleet v4.92.0.