CVE-2026-23518
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 · uneditedFleet is open source device management software. In versions prior to 4.78.3, 4.77.1, 4.76.2, 4.75.2, and 4.53.3, a vulnerability in Fleet's Windows MDM enrollment flow could allow an attacker to submit forged authentication tokens that are not properly validated. Because JWT signatures were not verified, Fleet could accept attacker-controlled identity claims, enabling enrollment of unauthorized devices under arbitrary Azure AD user identities. Versions 4.78.3, 4.77.1, 4.76.2, 4.75.2, and 4.53.3 fix the issue. 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 confidenceA critical authentication bypass vulnerability existed in Fleet's Windows MDM enrollment flow where JWT signatures were not validated. This allowed attackers to forge authentication tokens and enroll unauthorized devices under arbitrary Azure AD user identities by submitting attacker-controlled identity claims that Fleet would accept without verification.
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< 4.53.3>= 4.75.0, < 4.75.2>= 4.76.0, < 4.76.2>= 4.78.0, < 4.78.3= 4.77.0CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Identify installed Fleet versionRun 'fleetctl --version' or check the Fleet UI dashboard version indicator, or inspect the Docker container or binary version if self-hostedAffected if Version is < 4.53.3, OR >= 4.75.0 and < 4.75.2, OR >= 4.76.0 and < 4.76.2, OR >= 4.78.0 and < 4.78.3, OR exactly 4.77.0
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Confirm Windows MDM enrollment is enabledNavigate to Fleet settings > MDM settings > Windows MDM, or query the API endpoint /api/v1/fleet/mdm/windows for the windows_mdm_enabled configuration flagAffected if Windows MDM enrollment feature is turned on in the Fleet instance
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Verify MDM integration configurationCheck Fleet's MDM settings for Azure AD integration - inspect the MDM Microsoft Graph API registration status and confirm whether the Windows MDM root certificate is configuredAffected if Windows MDM is configured with Azure AD integration for device enrollment
A Fleet instance is affected if it runs a vulnerable version (listed above) AND has Windows MDM enrollment enabled with Azure AD integration, allowing unauthenticated enrollment via forged JWT tokens.
Generated from the published advisory. Verify against your own configuration.
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 · scoped4.53.34.75.24.76.2
Upgrade Fleet to version 4.78.3, 4.77.1, 4.76.2, 4.75.2, or 4.53.3 or later to implement proper JWT signature verification. If immediate patching is not feasible, temporarily disable Windows MDM enrollment as a compensating control.
Upgrade to 4.78.3 (or 4.77.1, 4.76.2, 4.75.2, or 4.53.3 depending on your current version branch)
- 1. Identify the current Fleet version by checking the Fleet dashboard or running `fleetctl version`
- 2. Determine which version branch your installation is on (4.53.x, 4.75.x, 4.76.x, or 4.78.x)
- 3. For version 4.53.x: Upgrade to version 4.53.3
- 4. For version 4.75.x: Upgrade to version 4.75.2
- 5. For version 4.76.x: Upgrade to version 4.76.2
- 6. For version 4.78.x: Upgrade to version 4.78.3
- 7. If upgrading to a fixed release is not immediately possible, disable Windows MDM enrollment as a temporary mitigation via Fleet settings
- 8. After upgrading, verify that JWT signature verification is working correctly in the Windows MDM enrollment flow
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-23518 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-23518 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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