CVE-2026-23999: Fleet: Device lock PIN can be predicted if lock time is known
Summary
Fleet generated device lock and wipe PINs using a predictable algorithm based solely on the current Unix timestamp. Because no secret key or additional entropy was used, the resulting PIN could potentially be derived if the approximate time the device was locked is known.
Impact
Fleet’s device lock and wipe commands generate a 6-digit PIN that is displayed to administrators for unlocking a device. In affected versions, this PIN was deterministically derived from the current timestamp.
An attacker with physical possession of a locked device and knowledge of the approximate time the lock command was issued could theoretically predict the correct PIN within a limited search window.
However, successful exploitation is constrained by multiple factors: - Physical access to the device is required. - The approximate lock time must be known. - The operating system enforces rate limiting on PIN entry attempts. - Attempts would need to be spread over multiple days. - Device wipe operations would typically complete before sufficient attempts could be made.
As a result, this issue does not allow remote exploitation, fleet-wide compromise, or bypass of Fleet authentication controls.
Workarounds
There are no known workarounds for this issue. Customers should upgrade to a patched version.
For more information
If there are any questions or comments about this advisory:
Email Fleet at security@fleetdm.com Join #fleet in osquery Slack
Credits
Fleet thanks @secfox-ai for responsibly reporting this issue.
Other sources
Fleet is open source device management software. In versions prior to 4.80.1, Fleet generated device lock and wipe PINs using a predictable algorithm based solely on the current Unix timestamp. Because no secret key or additional entropy was used, the resulting PIN could potentially be derived if the approximate time the device was locked is known. Fleet’s device lock and wipe commands generate a 6-digit PIN that is displayed to administrators for unlocking a device. In affected versions, this PIN was deterministically derived from the current timestamp. An attacker with physical possession of a locked device and knowledge of the approximate time the lock command was issued could theoretically predict the correct PIN within a limited search window. However, successful exploitation is constrained by multiple factors: Physical access to the device is required, the approximate lock time must be known, the operating system enforces rate limiting on PIN entry attempts, attempts would need to be spread over, and device wipe operations would typically complete before sufficient attempts could be made. As a result, this issue does not allow remote exploitation, fleet-wide compromise, or bypass of Fleet authentication controls. Version 4.80.1 contains a patch. No known workarounds are available.
— MITRE
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-23999?
CVE-2026-23999 is considered a moderate vulnerability due to the potential for unauthorized access resulting from predictable device lock PINs.
How do I fix CVE-2026-23999?
To fix CVE-2026-23999, upgrade to Fleet version 4.80.1 or later, where the PIN generation algorithm has been improved.
What versions of Fleet are affected by CVE-2026-23999?
Fleet versions prior to 4.80.1 are affected by CVE-2026-23999, making them vulnerable to the predictable PIN generation issue.
What does CVE-2026-23999 mean for device security?
CVE-2026-23999 means that if the lock time is known, attackers might predict the device lock PIN, compromising device security.
Is there a workaround for CVE-2026-23999 before upgrading?
There is no official workaround for CVE-2026-23999, and upgrading is the recommended solution to mitigate the risk.