AT&T WinVNC Remote Desktop Default Configuration Vulnerability
BID:1961
Info
AT&T WinVNC Remote Desktop Default Configuration Vulnerability
| Bugtraq ID: | 1961 |
| Class: | Configuration Error |
| CVE: | |
| Remote: | Yes |
| Local: | Yes |
| Published: | Nov 19 2000 12:00AM |
| Updated: | Nov 19 2000 12:00AM |
| Credit: | This vulnerability was first reported to Bugtraq by Gossi <[email protected]> on November 19, 2000. |
| Vulnerable: |
AT&T WinVNC 3.3 x |
| Not Vulnerable: | |
Discussion
AT&T WinVNC Remote Desktop Default Configuration Vulnerability
AT&T WinVNC (Virtual Network Computing) is a freeware package available from AT&T Labs Cambridge that allows an existing desktop of a PC to be remotely available.
During WinVNC's default install process, a registry key is created that could allow a remote attacker to modify the registry entry and allow un-authenticated access to the service. The registry key - HKEY_LOCAL_MACHINE\Software\ORL\WinVNC3\ - contains the connection password, IP and query restrictions as well as other settings. By default, this key is created during install with "Administrator" and "SYSTEM" accounts having full control and the "Everybody" account having Special Access (read and modify). Please note that under Windows 2000, this key has "Standard User" privileges which can accomplish the same thing.
While it is possible for a remote attacker to exploit this using regedit (blank the password value and set the "AuthRequired" key to 0) the machine needs to be a NT 4.0 system missing the registry permission patch. If the machine is patched or is Windows 2000, you must have administrator rights or equivalent to gain access from the network. If successful, a remote attacker could gain complete access to the system.
AT&T WinVNC (Virtual Network Computing) is a freeware package available from AT&T Labs Cambridge that allows an existing desktop of a PC to be remotely available.
During WinVNC's default install process, a registry key is created that could allow a remote attacker to modify the registry entry and allow un-authenticated access to the service. The registry key - HKEY_LOCAL_MACHINE\Software\ORL\WinVNC3\ - contains the connection password, IP and query restrictions as well as other settings. By default, this key is created during install with "Administrator" and "SYSTEM" accounts having full control and the "Everybody" account having Special Access (read and modify). Please note that under Windows 2000, this key has "Standard User" privileges which can accomplish the same thing.
While it is possible for a remote attacker to exploit this using regedit (blank the password value and set the "AuthRequired" key to 0) the machine needs to be a NT 4.0 system missing the registry permission patch. If the machine is patched or is Windows 2000, you must have administrator rights or equivalent to gain access from the network. If successful, a remote attacker could gain complete access to the system.
Exploit / POC
AT&T WinVNC Remote Desktop Default Configuration Vulnerability
Please see discussion.
Please see discussion.
Solution / Fix
AT&T WinVNC Remote Desktop Default Configuration Vulnerability
Solution:
Administrators should use Regedit to remove the "Everybody" and "Standard Users" permissions from the registry key entry.
To aid in the prevention of a remote comprimise (NT 4.0), ensure that the Registry Permission patch has been applied and restrict access to the registry.
Solution:
Administrators should use Regedit to remove the "Everybody" and "Standard Users" permissions from the registry key entry.
To aid in the prevention of a remote comprimise (NT 4.0), ensure that the Registry Permission patch has been applied and restrict access to the registry.
References
AT&T WinVNC Remote Desktop Default Configuration Vulnerability
References:
References:
- Virtual Network Computing (AT&T Laboratories Cambridge)