In Jenkins 2.587 and earlier, LTS 2.580.1 and earlier, the HTTP endpoint for creating the first user account does not check whether the setup wizard h

Summary

In Jenkins 2.587 and earlier, LTS 2.580.1 and earlier, the HTTP endpoint for creating the first user account does not check whether the setup wizard has been completed, resulting in a race condition that allows unauthenticated attackers to create an administrator account while the initial user account is being replaced.

Remediation

1. Inventory every Jenkins Jenkins deployment, including staging.
2. Upgrade Jenkins Jenkins to the fixed version for your release line, listed under Affected versions.
3. Confirm the running version after the upgrade.

References

• Advisoryhttps://www.jenkins.io/security/advisory/2026-10-28/#SECURITY-4122