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FleetApplication · Fleetdm

CVE-2026-26191

CRITICAL · 9.8 CVSS v3.1 Published 2026-05-14
Fix available
A fix is available. Upgrade to 4.81.0 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

In Fleet versions prior to 4.81.0, metadata extracted from uploaded software packages (.pkg, .deb, .rpm, .exe, .msi) is not sanitized before insertion into auto-generated uninstall scripts. Attackers can embed shell commands in package metadata fields, achieving arbitrary command execution as root (macOS/Linux) or SYSTEM (Windows) when the uninstaller runs on managed endpoints.

MitigationUpgrade to Fleet 4.81.0 or later. Until upgrade is possible, avoid uploading software from untrusted sources and manually inspect/edit auto-generated uninstall scripts before deployment.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
FleetApplication
Affected:< 4.81.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Determine Fleet server version
    Access the Fleet UI and check the version number displayed in the footer or navigation, or run 'fleetctl version' on the server if you have CLI access
    Affected if The installed version is below 4.81.0
  2. Identify uploaded software packages
    In Fleet UI, navigate to the Software inventory page and review the list of deployed software packages. Check if any packages were uploaded with .pkg, .deb, .rpm, .exe, or .msi extensions
    Affected if Any software packages with these extensions have been uploaded to Fleet
  3. Locate auto-generated uninstall scripts
    In Fleet UI, go to the Software details for each uploaded package and examine the 'Uninstall script' field. Look for the presence of metadata variables (such as package name, version, or vendor) being inserted directly into the script without escaping
    Affected if Uninstall scripts contain raw metadata values concatenated into shell commands, especially for packages uploaded from untrusted sources
  4. Verify package upload source
    Review the software package metadata and source for each uploaded item. Check if any .pkg, .deb, .rpm, .exe, or .msi packages originated from untrusted or third-party sources
    Affected if Software packages from untrusted sources have been uploaded and contain custom metadata that could include shell metacharacters

You are affected if running Fleet version below 4.81.0 AND you have uploaded .pkg, .deb, .rpm, .exe, or .msi software packages whose uninstall scripts contain unsanitized metadata from those packages.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 4.81.0 or later
Fixed in 4.81.0
Interim mitigation

Upgrade to Fleet 4.81.0 or later. Until upgrade is possible, avoid uploading software from untrusted sources and manually inspect/edit auto-generated uninstall scripts before deployment.

Recommended fix High confidence

Fleet version 4.81.0

  1. 1. Back up your current Fleet configuration and database to ensure data safety before upgrading
  2. 2. Review the Fleet upgrade documentation for your deployment method (e.g., Kubernetes, Docker, RPM/DEB packages)
  3. 3. Upgrade Fleet to version 4.81.0 or later using your standard upgrade procedure
  4. 4. After upgrading, verify the Fleet server is functioning correctly by logging in and checking core features
  5. 5. If immediate upgrade is not possible: implement bothworkarounds - (a) only upload software packages from trusted/verified sources, and (b) always manually inspect and edit auto-generated uninstall scripts before deployment
  6. 6. Audit existing software packages in Fleet to identify any that may have been uploaded from untrusted sources prior to the patch

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Fleet Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,040
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-26191 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data