Microsoft's monthly patch train got back on track yesterday with the release of a fix for a potentially devastating security vulnerability involving a core component of Windows.
The buffer overrun bug with Microsoft's Abstract Syntax Notation 1 (ASN.1) library could be exploited to seize control of vulnerable systems.
"An attacker who successfully exploited this buffer overflow vulnerability could execute code with system privileges on an affected system. The attacker could then take any action on the system, including installing programs, viewing data, changing data, deleting data, or creating new accounts with full privileges," Microsoft warns.
Windows 2000/XP/2003 are all affected by the vulnerability, which was discovered by security researchers at eEye six months ago.
Since then Microsoft has been working on a fix, which was finally released yesterday. Redmond has described the fix as "critical" - its highest security rating - and is urging users to apply its patch immediately.
This - if anything - is understating things since this vulnerability is probably the worst to surface since the RPC subsystem flaws (which are exploited by worms such as Blaster).
The latest flaw could have allowed crackers to break into their vulnerable computers to perform any manner of mischief over the last six months. However neither eEye nor Microsoft are aware of malicious exploitation of the vuln.
And another thing...
As part as its monthly patch cycle, Microsoft also released fixes for two less serious security problems (both described by Redmond as "important").
These are: a flaw in the Windows Internet Naming Service (WINS) that could allow hostile code to be injected into vulnerable systems; and a flaw in Virtual PC for Mac, which might allow privilege elevation.
Microsoft's latest batch of security patches follows a cumulative fix for IE released earlier this month outside the normal patch cycle. This fix dropped support for a common Web authentication method to fix a flaw which made it easier to lure IE users to malicious constructed or fraudulent sites.
None of these fixes has anything to do with the ongoing spread of MyDoom, which is due to cease tomorrow. ®