Is there a patch available for CVE-2026-26191?

Yes, a patch is available for CVE-2026-26191. Update the affected software to the latest version immediately.

Fleet CVE-2026-26191

Q: What is the CVSS score of CVE-2026-26191?

CVE-2026-26191 has a CVSS 4.0 base score of 6.0 (Medium). CVSS vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/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. EPSS exploitation probability: 0.1%.

EUVD-2026-30376 MEDIUM

OS Command Injection (CWE-78)

2026-05-14 https://github.com/fleetdm/fleet

GHSA-9vcr-g537-3w5v

Microsoft Apple Command Injection

6.0

CVSS 4.0 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

6.0 MEDIUM

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

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Scope

Lifecycle Timeline

Patch available

May 14, 2026 - 21:32 EUVD

CVSS changed

May 14, 2026 - 20:22 NVD

6.0 (MEDIUM)

Source Code Evidence Fetched

May 14, 2026 - 14:03 vuln.today

Analysis Generated

May 14, 2026 - 14:03 vuln.today

CVE Published

May 14, 2026 - 13:17 nvd

MEDIUM

DescriptionGitHub Advisory

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)](mailto:security@fleetdm.com)

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Credits

We thank @secfox-ai for responsibly reporting this issue.

AnalysisAI

OS command injection in Fleet's software installer pipeline allows arbitrary code execution as root (macOS/Linux) or SYSTEM (Windows) on managed endpoints when a specially crafted software package is uninstalled. The vulnerability exists because package metadata fields are not sanitized before being incorporated into auto-generated uninstall scripts. An attacker with the ability to upload packages to Fleet can exploit this by embedding malicious commands in package metadata fields, resulting in code execution with elevated privileges when endpoints execute the uninstall operation. Patch version 4.81.1 available.

Technical ContextAI

Fleet extracts metadata from software package binaries (.pkg, .deb, .rpm, .exe, .msi) during upload to the software installer pipeline and uses this metadata to automatically generate platform-specific uninstall scripts. The vulnerability is rooted in CWE-78 (OS Command Injection), a class of flaws where untrusted input derived from package metadata is concatenated directly into shell commands without proper escaping or sanitization. macOS packages (.pkg) and Linux packages (.deb, .rpm) generate shell scripts that execute with root privileges, while Windows packages (.exe, .msi) generate scripts executing as SYSTEM. The lack of input validation on package metadata fields (such as package name, version, or description fields embedded in the package binary) allows an attacker to inject shell metacharacters or command separators that alter the intended behavior of the uninstall script when it executes on managed endpoints.

RemediationAI

Upgrade Fleet to version 4.81.1 or later immediately. The fix sanitizes package metadata before inclusion in generated uninstall scripts. Until an upgrade is possible, implement compensating controls: restrict package upload permissions to a minimal set of trusted administrators with strong authentication, manually inspect all auto-generated uninstall scripts within the Fleet UI before deploying them to endpoints, and avoid uploading software packages from untrusted or unverified sources. The manual inspection workaround adds administrative overhead but allows continued use of the software installer feature with reduced risk. Refer to the Fleet 4.81.1 release notes at https://github.com/fleetdm/fleet/releases/tag/fleet-v4.81.1 and the security advisory at https://github.com/fleetdm/fleet/security/advisories/GHSA-9vcr-g537-3w5v for detailed upgrade instructions.