CVE-2026-34389: Fleet's user account creation via invite does not enforce invited email address
Summary
Fleet contained an issue in the user invitation flow where the email address provided during invite acceptance was not validated against the email address associated with the invite. An attacker who obtained a valid invite token could create an account under an arbitrary email address while inheriting the role granted by the invite, including global admin.
Impact
If an attacker gains access to a valid invite token, they can create a Fleet user account with an email address of their choosing while inheriting the invite’s assigned role and team memberships.
This issue:
- Requires possession of a valid invite token - Does not bypass authentication controls beyond invite-based account creation - Does not expose data without successful account creation
Workarounds
If upgrading immediately is not possible:
- Treat invite links as sensitive credentials and avoid sharing them in public or semi-public channels (e.g., Slack, Teams). - Revoke and reissue invites if there is any concern that an invite link may have been exposed. - Prefer issuing invites with the minimum required privileges and elevating roles after account creation when appropriate.
For more information
If there are any questions or comments about this advisory:
Send an email to security@fleetdm.com
Credits
Fleet thanks @fuzzztf for responsibly reporting this issue.
Other sources
Fleet is open source device management software. Prior to 4.81.0, Fleet contained an issue in the user invitation flow where the email address provided during invite acceptance was not validated against the email address associated with the invite. An attacker who obtained a valid invite token could create an account under an arbitrary email address while inheriting the role granted by the invite, including global admin. Version 4.81.0 patches the issue.
— NVD
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-34389?
CVE-2026-34389 has been classified as a critical vulnerability due to its potential for unauthorized access.
How do I fix CVE-2026-34389?
To mitigate CVE-2026-34389, update to Fleet version 4.81.0 or later where the email validation issue is resolved.
What systems are affected by CVE-2026-34389?
CVE-2026-34389 affects Fleet versions prior to 4.81.0.
What type of attack can CVE-2026-34389 facilitate?
CVE-2026-34389 can allow attackers to create user accounts without validating email addresses, potentially leading to unauthorized access.
Is user email validation mandatory to address CVE-2026-34389?
Yes, enforcing user email validation is crucial to prevent the exploitation of CVE-2026-34389.