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.

Published · last modified .

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.

EPSS exploit prediction

EPSS: 0.003 (15.7th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 16th percentile — 15.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-23518: held from 0.002 to 0.003.

EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.000

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

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.