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.

Source published

27 Sep 2026 17:02:34 UTC

Source modified

30 Sep 2026 17:20:13 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 4.0 · 8.9 CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

CVSS 3.1 · 8.0 CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H