Microsoft WinNT 'Syskey Keystream Reuse' Vulnerability patch - Version 1 Microsoft has released a patch that eliminates a vulnerability in Syskey, a utility that provides additional protection for Microsoft(r) Windows NT password databases. The vulnerability allows a particular cryptanalytic attack to be effective against Syskey, significantly reducing the strength of the protection it offers. The patch eliminates the vulnerability and restores strong protection to the password database.