Stack-based buffer overflow in msiexec.exe 3.1.4000.1823 and 4.5.6001.22159 in Microsoft Windows Installer allows context-dependent attackers to execute arbitrary code via a long GUID value for the /x (aka /uninstall) option.  NOTE: this issue might cross privilege boundaries if msiexec.exe is reachable via components such as ActiveX controls, and might additionally require a separate vulnerability in the control.