CVE-2026-26191 is a medium-severity OS command injection vulnerability in github.com/fleetdm/fleet/v4 (go), affecting versions < 4.81.1. It is fixed in 4.81.1.
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 [[email protected]](mailto:[email protected]) 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.
Untrusted input reaches a shell command, allowing arbitrary commands to run on the host. Typical impact: code execution in the application's environment.
go
github.com/fleetdm/fleet/v4 (< 4.81.1)github.com/fleetdm/fleet/v4 → 4.81.1 (go)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter instead of chasing every advisory.
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Already deployed Kodem? See CVE-2026-26191 in your environment →Upgrade github.com/fleetdm/fleet/v4 to 4.81.1 or later to resolve this vulnerability.
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CVE-2026-26191 is a medium-severity OS command injection vulnerability in github.com/fleetdm/fleet/v4 (go), affecting versions < 4.81.1. It is fixed in 4.81.1. Untrusted input reaches a shell command, allowing arbitrary commands to run on the host.
github.com/fleetdm/fleet/v4 (go) versions < 4.81.1 is affected.
Yes. CVE-2026-26191 is fixed in 4.81.1. Upgrade to this version or later.
Whether CVE-2026-26191 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
Upgrade github.com/fleetdm/fleet/v4 to 4.81.1 or later.