CVE-2026-23518

Fleet has a JWT signature bypass vulnerability in Azure AD MDM enrollment

State: Published
Severity: 9.3 Critical
Published: Jan 21, 2026
Updated: Jan 22, 2026
Reserved: Jan 13, 2026

Description

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.

Scores

CVSS	Score	Vector	Source
4.0	9.3 Critical	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N	GitHub_M

Weaknesses

CWE-347 Improper Verification of Cryptographic Signature

Affected Products

Product	Versions
fleetfleetdm	>= 4.78.0, < 4.78.3Affected >= 4.77.0, < 4.77.1Affected >= 4.76.0, < 4.76.2Affected >= 4.75.0, < 4.75.2Affected < 4.53.3Affected

References

Every record here comes from the CVE Program’s CVE List. © 1999–2026 The MITRE Corporation. CVE is a registered trademark of The MITRE Corporation. The records are reproduced under the CVE Program terms of use.