Incorrect Permission Assignment in TightVNC Server for Windows

Executive Summary

This vulnerability involves incorrect permission assignment in GlavSoft TightVNC Server for Windows before version 2.8.88. A local authenticated user can read or overwrite inter-process communication handles between the TightVNC service and its desktop server process due to a named shared memory segment created with a NULL DACL. The segment name is predictable, allowing low-privileged processes to tamper with the IPC channel of a SYSTEM service.

Useful 0 Not Useful 0

Detection Guidance

Check if TightVNC Server for Windows is installed and verify the version is 2.8.88 or later. Inspect running services for 'TightVNC Server' and review shared memory segments in the Global namespace for NULL DACL permissions. Use tools like Process Explorer to monitor IPC handles and named objects.

Useful 0 Not Useful 0

Impact Analysis

This vulnerability can lead to disclosure of session data, privilege escalation, or denial of service. An attacker could exploit it to gain higher privileges, access sensitive information, or disrupt the TightVNC service running as SYSTEM.

Useful 0 Not Useful 0

Mitigation Strategies

Update TightVNC Server to version 2.8.88 or later immediately. Restrict local user permissions to prevent unauthorized access to shared memory segments. Monitor for unusual IPC handle tampering or service behavior changes.

Useful 0 Not Useful 0