Peter Winter-Smith of NGSSoftware has discovered a high risk vulnerability in the Microsoft Windows Remote Access Connection Manager (RASMAN) service which (under certain versions of the OS) can allow a remote, anonymous attacker to gain complete control over a vulnerable system. The vulnerability is specific to one of the RPC interfaces provided by the RASMAN service. A sequence of specially crafted RPC calls to a given function exposed through the interface can lead to registry corruption, which can - in turn - lead to stack memory corruption within the Service Host instance hosting the RASMAN service. Under a default install of Windows 2000 SP4 the vulnerability can be reached by an anonymous user, under Windows XP SP2 and Windows 2003 Server the vulnerability can only be used for local privilege elevation. This issue has been resolved in the Microsoft security bulletin MS06-025 which can be downloaded from: http://www.microsoft.com/technet/security/Bulletin/MS06-025.mspx NGSSoftware are going to withhold details of this flaw for three months. Full details will be published on the 13th September 2006. This three month window will allow users of Microsoft Windows the time needed to apply the patch before the details are released to the general public. This reflects NGSSoftware's approach to responsible disclosure. NGSSoftware Insight Security Research http://www.ngssoftware.com http://www.databasesecurity.com/ http://www.nextgenss.com/ +44(0)208 401 0070