CVE-2026-26191: Fleet vulnerable to OS command injection in software packages
Summary
A vulnerability in Fleet's software installer pipeline could allow a crafted software package to execute arbitrary commands as root (macOS/Linux) or SYSTEM (Windows) on managed endpoints when an uninstall is triggered.
Impact
When a software package (.pkg, .deb, .rpm, .exe, or .msi) is uploaded to Fleet, metadata is extracted from the package binary and used to generate uninstall scripts. In affected versions, this metadata is not properly sanitized before being included in the generated scripts. A specially crafted package containing malicious values in its metadata fields could result in unintended command execution when the uninstall script runs on managed endpoints.
Workarounds
If an immediate upgrade is not possible, administrators should avoid uploading software packages obtained from untrusted or unverified sources. Additionally, administrators can manually inspect and edit auto-generated uninstall scripts before deployment.
For more information
If you have any questions or comments about this advisory:
Email us at [security@fleetdm.com](mailto:security@fleetdm.com)
Join #fleet in [osquery Slack](https://join.slack.com/t/osquery/sharedinvite/zt-h29zm0gk-s2DBtGUTW4CFel0f0IjTEw)
Credits
We thank @secfox-ai for responsibly reporting this issue.
Other sources
Fleet is open source device management software. Prior to version 4.81.0, a vulnerability in Fleet's software installer pipeline could allow a crafted software package to execute arbitrary commands as root (macOS/Linux) or SYSTEM (Windows) on managed endpoints when an uninstall is triggered. When a software package (.pkg, .deb, .rpm, .exe, or .msi) is uploaded to Fleet, metadata is extracted from the package binary and used to generate uninstall scripts. In affected versions, this metadata is not properly sanitized before being included in the generated scripts. A specially crafted package containing malicious values in its metadata fields could result in unintended command execution when the uninstall script runs on managed endpoints. Version 4.81.0 contains a patch. If an immediate upgrade is not possible, administrators should avoid uploading software packages obtained from untrusted or unverified sources. Additionally, administrators can manually inspect and edit auto-generated uninstall scripts before deployment.
— MITRE
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-26191?
CVE-2026-26191 is considered a critical vulnerability due to its ability to allow arbitrary command execution as root or SYSTEM.
How do I fix CVE-2026-26191?
To mitigate CVE-2026-26191, you should update Fleet to version 4.81.1 or later.
What types of systems are affected by CVE-2026-26191?
CVE-2026-26191 affects macOS, Linux, and Windows systems using Fleet's software installer pipeline.
What is the impact of CVE-2026-26191?
CVE-2026-26191 could lead to malicious software packages executing arbitrary commands on managed endpoints.
Is CVE-2026-26191 an exploit for specific software packages?
Yes, CVE-2026-26191 affects crafted software packages such as .pkg, .deb, .rpm, .exe, or .ms.