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FleetApplication · Fleetdm

CVE-2026-23998

HIGH · 7.5 CVSS v3.1 Published 2026-05-14
Fix available
A fix is available. Upgrade to 4.81.0 or later.
See remediation →
84/100
Remediation priority · High
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 Windows MDM management endpoint could allow requests to be processed without proper client certificate validation. In certain circumstances, this could allow an attacker to impersonate an enrolled Windows device and retrieve sensitive configuration data. Fleet’s Windows MDM management endpoint relies on mutual TLS (mTLS) client certificates to authenticate enrolled devices. In affected versions, requests that did not present a client certificate could be incorrectly treated as trusted. As a result, an attacker with prior knowledge of a valid enrolled device identifier could potentially impersonate that device and receive configuration payloads intended for it. These payloads may contain sensitive information such as Wi-Fi or VPN configuration data, certificates, or other secrets delivered through MDM profiles. This issue does not allow enrollment of new devices, administrative access to Fleet, or compromise of the Fleet control plane. Impact is limited to the targeted Windows device. Version 4.81.0 contains a patch. If an immediate upgrade is not possible, affected Fleet users should temporarily disable Windows MDM.

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

A logic error in Fleet's Windows MDM endpoint allows requests without client certificates to bypass mTLS validation. Attackers with knowledge of a valid enrolled device identifier can impersonate that device and retrieve sensitive MDM configuration payloads containing Wi-Fi credentials, VPN settings, certificates, or other secrets.

MitigationUpgrade to Fleet version 4.81.0 or later to apply the patch. If immediate upgrade is not feasible, temporarily disable the Windows MDM functionality as a compensating control.

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
None
Availability
None

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

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. Check Fleet version
    Run 'fleetctl version' or check the Fleet server's about page to determine the installed Fleet version
    Affected if The installed version is earlier than 4.81.0
  2. Verify Windows MDM is enabled
    Check Fleet's configuration settings or documentation to confirm the Windows MDM feature is active in your deployment
    Affected if Windows MDM functionality is enabled in the Fleet instance
  3. Inspect MDM endpoint accessibility
    Examine whether the Windows MDM API endpoints are exposed and reachable without requiring client certificate authentication
    Affected if The MDM endpoints accept requests without validating client certificates
  4. Review device enrollment logs
    Check Fleet's MDM enrollment and request logs for any suspicious device authentication patterns or unexpected device identifiers
    Affected if There are enrollment requests using valid device identifiers without proper certificate-based authentication
  5. Audit MDM configuration payload access
    Review logs or access records for MDM configuration payloads containing Wi-Fi credentials, VPN settings, or certificates that may have been retrieved
    Affected if Configuration payloads were retrieved by devices without valid client certificate authentication

You are affected if Fleet version is below 4.81.0 AND Windows MDM is enabled, as the logic error allows impersonation of enrolled devices without client certificate validation.

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 version 4.81.0 or later to apply the patch. If immediate upgrade is not feasible, temporarily disable the Windows MDM functionality as a compensating control.

Recommended fix High confidence

Fleet version 4.81.0

  1. Backup your current Fleet configuration and database
  2. Verify current Fleet version is below 4.81.0
  3. Upgrade Fleet to version 4.81.0 using your deployment method (Docker, Kubernetes Helm, or package manager)
  4. After upgrade, verify the Windows MDM endpoint is accepting client certificates correctly by testing mTLS authentication
  5. Confirm the version upgrade was successful by checking the Fleet UI or API version endpoint
  6. Monitor logs for any authentication errors related to Windows MDM client certificates

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

Fix this in Fleet Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing8.0 h
  • Review / QA4.0 h
20.0 hours of engineering $3,440
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,504.

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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-2026-23998 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