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[ISN] Windows Small Business Server at risk from critical flaw


By Robert McMillan
IDG News Service
January 24, 2008

Microsoft said Wednesday that another one of its operating system 
products is vulnerable to a critical vulnerability, first patched two 
weeks ago.

In an update to its MS08-001 security bulletin, Microsoft said that the 
latest release of Windows Small Business Server was also critically at 
risk from a bug in Windows' networking software.

The flaw is also considered critical for Windows XP and Vista users. 
Microsoft did not say why it had initially omitted Small Business Server 
from its list of critically affected operating systems, but it said that 
the product's users were being offered patches via Microsoft's various 
automatic update services. "Customers with Windows Small Business Server 
2003 Service Pack 2 should apply the update to remain secure," Microsoft 
said in its updated bulletin.

The bug lies in the way Windows processes networking traffic that uses 
IGMP (Internet Group Management Protocol) and MLD (Multicast Listener 
Discovery) protocols, which are used to send data to many systems at the 
same time. Microsoft said that an attacker could send specially crafted 
packets to a victim's machine, which could then allow the attacker to 
run unauthorized code on a system.

Microsoft rates the flaw as "important" for Windows Server 2003, meaning 
that it would be more difficult for attackers to exploit the flaw on 
this operating system.

Security experts are paying particular attention to this vulnerability 
because it could be exploited by attackers to create a self-replicating 
worm attack.

The flaw is not being exploited in online attacks, but last week 
researchers at penetration-testing-software vendor Immunity made a 
sample exploit available to their customers. That software causes an 
unpatched system to crash, but the company is close to developing code 
that could be used to install unauthorized software on a victim's 
computer, according to Immunity chief technology officer Dave Aitel.

Aitel said it's no surprise that the small business version of Windows 
Server 2003 is at risk.

"I assumed most 2003 servers in the real world were vulnerable," he said 
via instant message. "Windows Server 2003 by default does not have any 
multicast addresses active and would not be affected by this 
vulnerability. However, installing applications that use multicasting 
could cause the operating system to become vulnerable."

He said that Microsoft could help its customers by giving them more 
details on how to avoid being at risk to this problem. "What features 
can I enable on Windows Server 2003 to become vulnerable?" he asked.

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