Microsoft is working with Macrovision to check out a flaw in a driver on Windows Server 2003 and Windows XP that's being exploited in the wild, according to a Microsoft special security advisory released after business hours on Nov. 5. The danger is complete system takeover.
The vulnerability is in the Macrovision secdrv.sys driver on supported editions of Windows Server 2003 and Windows XP. The affected product is Macrovision SafeDisc, a copy-protection application written for Windows.
Microsoft said in security advisory 944653 that Vista is immune.
FrSRT reported on Oct. 19 that the trouble is a memory corruption error in the Macrovision Security Driver when processing user-supplied data. The vulnerability can be used by local attackers to gain so-called Ring 0 privileges and take complete control of an affected system.
That's bad. The term "Ring" refers to a protection ring of one or more hierarchical levels of privilege, with Ring 0 being the level with the most privileges and interacting the most directly with physical hardware, including the CPU and memory.
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The zero-day flaw has been publicly disclosed. Symantec on Oct. 22 updated its original (Oct. 18) Deep Sight security advisory to warn customers that a functional exploit had been made commercially available through Core Impact, an enterprise security testing product from Core Security.
The vulnerability is also being exploited in the wild. Microsoft reports that its customers are reporting "limited attacks."
In a successful exploit, an attacker would need to gain local, interactive access to a computer running the affected application. He or she would then need to create malicious code designed to carry out some actions on their behalf and would then have to interact with the affected driver to leverage the issue.
The attacker's code then runs with system-level privileges, according to Symantec's advisory, completely compromising affected systems.
Symantec is giving the vulnerability its highest impact rating of 10, but, given that this zero-day has to be triggered by a local user, the security company has pegged the severity at only 6.5 and the urgency rating at 6.6.
Macrovision now has an update out for supported versions of Windows Server 2003 and Windows XP.
Symantec suggests mitigating risk by giving only trusted users local access to computers. The company is also advising the use of restricted environments and restricted shells wherever possible.
Also, Symantec recommends modifying default ACL settings, ensuring that all applications have file system ACL permissions set according to security policy and that users avoid giving unauthorized users access to critical files or paths.
Microsoft said in its advisory that after it completes its investigation it will take appropriate action to protect customers, including providing a security update through its monthly Patch Tuesday release.
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