The researchers passed illegal PrefixLength values to routing tables using the CreateIpForwardEntry2 method. It corrupted Vista's kernel space memory, they explained.
"When adding a route entry to the IPv4 routing table using the method CreateIpForwardEntry2 and passing an illegal value greater than 32  for the destination PrefixLength member in the DestinationPrefix structure contained in the MIB_IPFORWARD_ROW2 structure , kernel space memory is being corrupted resulting in random blue screen crashes," wrote Thomas Unterleitner, a member of Phion's research team.
The team had used a program to corrupt Vista's memory. However, they also tried passing illegal values using the "route add" command and got the same results.
The problem affects security at the client level and could enable code injection, according to Unterleitner. However, the exploit requires administrative privileges to carry it out. A spokesperson for the Microsoft Security Response Center said in an e-mailed response that they were unaware of any affects on customers.
"To exploit the vulnerability, the attacker would have to already be a privileged user on the system; either an Administrator or part of the network administrator's group, which limits the impact of this attack to users that already have a high-level of trust on the system," the spokesperson wrote.
Phion first informed Microsoft of the problem on Oct. 22. The company is providing a workaround solution for users of its netfence entegra client security solution. However, Microsoft's spokesperson wrote that the company can't vouch for "third party security updates or mitigations."
The Microsoft spokesperson did not say when the company planned to issue a fix, but Unterleitner told ZDNet UK that "Microsoft will ship a fix for this exploit with the next Vista service pack."
Windows Vista Service Pack 2 Beta was released to private testers in late October, but the final release awaits meeting certain quality improvements, according to Mike Nash, Microsoft's corporate vice president for Windows product management, in an announcement. No date for Vista SP 2 is specified as yet.
The exploit affected Vista Enterprise and Vista Ultimate editions, but it likely affects other Vista versions, Unterleitner wrote. Windows XP is not subject to this buffer-overflow security problem.
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