Fleet, an open source device management tool, prior to version 4.82.0, improperly validates Azure AD JWT tokens in its Windows MDM enrollment flow. While it verifies token signatures via Microsoft's multi-tenant JWKS endpoint, it fails to enforce the 'aud' (audience) and 'iss' (issuer) claims. Consequently, any Microsoft-signed Azure AD access token with the expected scopes from any tenant can authenticate to Fleet's MDM endpoints. This enables attackers with access to any Azure AD tenant to enroll unauthorized devices and access Fleet's MDM management APIs. Additionally, Fleet may expose sensitive enrollment secrets embedded in MDM command payloads, increasing the risk of further unauthorized access. The vulnerability is tracked as CVE-2026-24899 with a CVSS 4.0 score of 8.2 (high severity). A patch is available in version 4.82.0. Fleet is a cloud service, so the vendor manages remediation for the cloud-hosted service.

An attacker with access to any Azure AD tenant can obtain a valid Microsoft-signed token and use it to bypass authentication in Fleet's Windows MDM enrollment flow. This allows unauthorized device enrollment and interaction with Fleet's MDM management APIs. Sensitive enrollment secrets may be exposed during device management, potentially enabling further unauthorized access. The vulnerability has a high severity rating (CVSS 8.2). There are no known exploits in the wild at this time.

A patch addressing this vulnerability is available in Fleet version 4.82.0. Users should upgrade to this version to remediate the issue. For those unable to upgrade immediately, temporarily disabling Windows MDM is recommended to prevent exploitation. Since Fleet is a cloud service, the vendor manages remediation for the cloud-hosted service; users should consult the vendor advisory for confirmation and further guidance.