CVE-2026-23518: Fleetdm Fleet

Critical severity, CVSS 9.8. EPSS: 0.3% chance of exploitation in the next 30 days.

Fleet 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.

Affected products

• Fleetdm Fleet: before 4.53.3 (fixed in 4.53.3); from 4.75.0, before 4.75.2 (fixed in 4.75.2); from 4.76.0, before 4.76.2 (fixed in 4.76.2); from 4.78.0, before 4.78.3 (fixed in 4.78.3); version 4.77.0 only

Published 2026-01-21. Last modified 2026-06-17.