A critical vulnerability (CVE-2020-11552) in ManageEngine ADSelfService Plus, an Active Directory password-reset solution, could allow attackers to remotely execute commands with system level privileges on the target Windows host.
About ManageEngine ADSelfService Plus
ManageEngine ADSelfService Plus is developed by ManageEngine, a division of Zoho Corporation, a software development company that focuses on web-based business tools and information technology.
“ADSelfService Plus supports self-service password reset for WFH and remote users by enabling users to reset Windows password from their own machines and updating the cached credentials through a VPN client,” the company touts.
It also supports sending password expiration notifications to remote users through email, SMS, and push notifications; provides admins with a way to force 2-factor authentication for Windows logons; and provides users with secure access to all SAML-supported enterprise applications (e.g., Office 365, G Suite, Salesforce) through AD-based single sign-on.
About the vulnerability (CVE-2020-11552)
Unearthed and flagged by Bhadresh Patel, CVE-2020-11552 stems from the solution not properly enforcing user privileges associated with Windows Certificate Dialog.
The ManageEngineADSelfService Plus thick client software enables users to perform a password reset or an account unlock action by using self-service option on the Windows login screen. When one of these options is selected, the client software is launched and connects to a remote ADSelfServicePlus server to facilitate the self-service operations.
“A security alert can/will be triggered when ‘an unauthenticated attacker having physical access to the host issues a self-signed SSLcertificate to the client’. Or, ‘a (default) self-signed SSLcertificate is configured on ADSelfService Plus server’,” he noted.
“‘ViewCertificate’ option from the security alert will allow an attacker with physical access or a remote attacker with RDP access, to export a displayed certificate to a file. This will further cascade to the standard dialog/wizard which will open file explorer as SYSTEM. By navigating file explorer through ‘C:\windows\system32\’, acmd.exe can be launched as a SYSTEM.”
Patel also published a PoC exploit video (the exploitation part starts at 5:30):
ManageEngine patched CVE-2020-11552 twice, because the first patch only fixed the issue partially. Admins are advised to upgrade to ADSelfService Plus build 6003, which contains the complete security fix.