Vulnerability in Fleetdm Fleet
CVE-2026-23518
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.
EPSS: 0.002 (13.5th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
Affected products
- Fleetdm Fleet — versions >= 4.75.0, < 4.75.2, >= 4.77.0, < 4.77.1, >= 4.78.0, < 4.78.3
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
Frequently asked questions
- What is CVE-2026-23518?
- CVE-2026-23518 is a critical-severity vulnerability in Fleetdm Fleet, classified under Improper Verification of Cryptographic Signature. CVSS score: 9.8/10. Published 2026-01-21.
- How severe is CVE-2026-23518?
- Critical severity. CVSS v3 base score is 9.8 out of 10.