CVE-2026-23518: Fleet has a JWT signature bypass vulnerability in Azure AD MDM enrollment
Summary 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.
Published Jan 20, 2026 · Updated Mar 27, 2026
Affected packages
github.com/fleetdm/fleet
- Ecosystem
- Go
- Affected
- >= 4.78.0, < 4.78.3
- Fixed in
- 4.78.3
- Check
go list -m github.com/fleetdm/fleet
github.com/fleetdm/fleet
- Ecosystem
- Go
- Affected
- >= 4.77.0, < 4.77.1
- Fixed in
- 4.77.1
- Check
go list -m github.com/fleetdm/fleet
github.com/fleetdm/fleet
- Ecosystem
- Go
- Affected
- >= 4.76.0, < 4.76.2
- Fixed in
- 4.76.2
- Check
go list -m github.com/fleetdm/fleet
github.com/fleetdm/fleet
- Ecosystem
- Go
- Affected
- >= 4.75.0, < 4.75.2
- Fixed in
- 4.75.2
- Check
go list -m github.com/fleetdm/fleet
github.com/fleetdm/fleet
- Ecosystem
- Go
- Affected
- < 4.43.5-0.20260112202845-e225ef57912c
- Fixed in
- 4.43.5-0.20260112202845-e225ef57912c
- Check
go list -m github.com/fleetdm/fleet
Advisory details
From the GitHub Advisory Database (CC BY 4.0).
Summary
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.
Impact
If Windows MDM is enabled, an attacker can enroll rogue devices by submitting a forged JWT containing arbitrary identity claims. Due to missing JWT signature verification, Fleet accepts these claims without validating that the token was issued by Azure AD, allowing enrollment under any Azure AD user identity.
Patches
- 4.78.3
- 4.77.1
- 4.76.2
- 4.75.2
- 4.53.3
Workarounds
If an immediate upgrade is not possible, affected Fleet users should temporarily disable Windows MDM.
For more information
If you have any questions or comments about this advisory:
Email us at [[email protected]](mailto:[email protected]) Join #fleet in osquery Slack
Credits
We thank @secfox-ai for responsibly reporting this issue.
Credited to prateek-0490, JordanMontgomery.
References
How this page is made: the data panel comes from the GitHub Advisory Database, CISA’s KEV catalog, the NVD and FIRST EPSS, and updates twice a day. No analysis has been written for this entry yet. Methodology