[ISN] Researchers Stymied By Microsoft Vulnerability

InfoSec News isn at c4i.org
Thu Jun 16 03:23:39 EDT 2005


By Gregg Keizer 
TechWeb News  
June 15, 2005   

Researchers on Wednesday were still dissecting one of the 
vulnerabilities patched by Microsoft Tuesday, and hadn't yet been able 
to "find the trick," said the head of one security firm's lab. 

Mike Murray, the director of research at vulnerability management
vendor nCircle, has had his entire team picking through the patch
provided by Microsoft to fix a flaw in Windows' SMB [1] (Server
Message Block) protocol, and hasn't yet been able to find a way to
exploit the vulnerability without going through authentication.

"It's incredible," said Murray. "We've found all the functions and the 
overflow, but we haven't been able to find the unauthenticated 
[attack] vector. We've found the authenticated vector, but as for the 
other, nope." 

nCircle pulls apart disclosed vulnerabilities to create new methods of 
vulnerability detection, and in the short term, to provide guidance to 
its customers on the relative danger of flaws in applications and 
operating systems, including Windows. 

According to Microsoft, the SMB vulnerability, which was laid out in
one of the ten security bulletins [2] released Tuesday, could be
exploited remotely by an attacker without requiring authentication, in
other words, without a legitimate Windows log-in username and

Such an unauthenticated attack avenue, experts warned Tuesday, made 
the bug much more dangerous, and could lead to a worm-style assault 
that attacked any computer with the SMB service exposed to the 

"There's a trick to this one," said Murray. When asked if it was good 
news that his team couldn't find the exploit -- that if they couldn't 
perhaps attackers might not either -- he said "It only takes one 
person to figure out that trick, and then it'll break wide open." 

Even though the nCircle research team has so far failed to puzzle out 
the SMB vulnerability, Murray still thinks that it's the most 
dangerous of the 12 announced yesterday. 

"It's still the most threatening, by far," said Murray. "In fact, 
there are two vulnerabilities, not just one," he said. "[The second] 
is strictly a denial-of-service vulnerability, a way to crash the SMB 
service through an uninitialized variable. Maybe Microsoft missed it, 
or didn't think of it as a true vulnerability, since it was the 
[buffer] overflow they concentrated on." 

Murray said his bunch would continue examining the vulnerability until 
they found a way to hack SMB sans authentication. "This is a tough nut 
to crack," he admitted. "Or maybe Microsoft was just throwing us a red 
herring telling us that it could be exploited unauthenticated." 

[1] http://www.microsoft.com/technet/security/Bulletin/MS05-027.mspx
[2] http://www.techweb.com/wire/security/164303082

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