EUVD-2026-87976
GHSA-v4vj-w767-q8qv
Severity by source
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
No Fleet creds needed (PR:N), but dual-review supply-chain gates make it AC:H; injection in Fleet's generator executes as root on separate managed hosts (S:C, C/I/A:H).
Primary rating from Vendor (VulnCheck).
CVSS VectorVendor: VulnCheck
Lifecycle Timeline
3DescriptionCVE.org
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.
AnalysisAI
OS command injection in Fleet's generator for Fleet-maintained macOS app install and uninstall scripts allows crafted Homebrew cask metadata containing shell metacharacters such as $(...) to be carried unescaped into scripts that run as root on managed macOS hosts. Manifests generated before 2026-08-19 are affected; the flaw is a supply-chain vector because the attacker needs no Fleet credentials, only the ability to land crafted metadata in an upstream Homebrew cask that must then survive both upstream Homebrew cask review and Fleet's review of the automated ingestion pull request before a managed host installs or uninstalls the app. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the attacker to land shell metacharacters (specifically command substitution such as $(...)) in the metadata of an upstream Homebrew cask that Fleet maintains an install/uninstall script for, and that crafted metadata must pass BOTH upstream Homebrew cask review AND Fleet's review of the automated ingestion pull request. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The vendor CVSS 4.0 score is 8.9 (high), but multiple signals argue for materially lower real-world priority. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Primary fix: upgrade to Fleet v4.92.0, which contains the ingestion-pipeline change (fleetdm/fleet#51324) that escapes cask metadata at every interpolation site; vendor advisory at https://github.com/fleetdm/fleet/security/advisories/GHSA-fv3p-h7wv-2jgm. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory all Fleet deployments and identify any Fleet-maintained macOS app install or uninstall scripts and manifests generated before 2026-08-19, then temporarily disable or suspend automatic ingestion of Homebrew cask updates into Fleet until a manual review step is in place. …
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Same weakness CWE-78 – OS Command Injection
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External POC / Exploit Code
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