# CVE-2026-26191: Fleet Device Management OS command injection in software installer pipeline

Source: https://junglewise.ai/threats/cve-2026-26191-fleet-device-management-os-command-injection-in-software  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-14. Updated: 2026-05-18  
License: CC BY 4.0 with a link back

CVE-2026-26191 · Severity: critical · CVSS 9.8 · Published 2026-05-14

Fleet is an open-source platform used by IT and security teams to manage and monitor laptops and servers. A vulnerability in how the system handles software installers could allow a malicious software package to take full control of managed computers. If an administrator uploads a specially crafted installer, the system may automatically generate and run malicious scripts with high-level administrative privileges (root or SYSTEM) when that software is later uninstalled.

Technologies: [github.com/fleetdm/fleet/v4 (Go)](https://junglewise.ai/threats/technologies/github-com-fleetdm-fleet-v4). Vendors: [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2026-26191 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-26191 being exploited in the wild.

**How severe is CVE-2026-26191?** Critical severity, with a CVSS score of 9.8, published 14 May 2026.

**Which products and versions are affected?** github.com/fleetdm/fleet/v4 (Go) < 4.81.1, SEMVER:introduced=0,fixed=4.81.1.

**Is there a fix for CVE-2026-26191?** Yes. github.com/fleetdm/fleet/v4 (Go): upgrade to 4.81.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-26191 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-26191?** Check whether you run github.com/fleetdm/fleet/v4 (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/fleetdm/fleet/v4 (Go): upgrade to 4.81.1 or later

  ```sh
  go get github.com/fleetdm/fleet/v4@v4.81.1
  ```


## Technical details

An OS command injection vulnerability (CWE-78) exists in Fleet's software installer pipeline. When software packages (such as .pkg, .deb, .rpm, .exe, or .msi) are uploaded, Fleet extracts metadata from the binaries to automatically generate uninstall scripts. This metadata is not properly sanitized before being embedded into the scripts. An attacker who can convince an administrator to upload a crafted package can achieve arbitrary command execution with root (macOS/Linux) or SYSTEM (Windows) privileges on managed endpoints when an uninstallation is triggered. The issue is resolved in version 4.81.1.

## Affected products

- Fleet Device Management (fleetdm) Fleet < 4.81.1

## Identifiers

- CVE-2026-26191
- GHSA-9vcr-g537-3w5v
- GO-2026-5301

## Timeline

- 2026-05-13: advisory: GitHub Security Advisory published
- 2026-05-14: disclosed: CVE published to NVD
- 2026-03-02: patched: Version 4.81.1 released

## References

- [https://github.com/fleetdm/fleet/releases/tag/fleet-v4.81.1](https://github.com/fleetdm/fleet/releases/tag/fleet-v4.81.1)
- [https://github.com/fleetdm/fleet/security/advisories/GHSA-9vcr-g537-3w5v](https://github.com/fleetdm/fleet/security/advisories/GHSA-9vcr-g537-3w5v)

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