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The first security bulletin, rated as "critical," affects all supported versions of Windows. The second, rated "important," affects Windows Vista. Attackers could exploit the vulnerabilities to execute remote code on a targeted computer. "As always, we recommend that customers deploy these updates as soon as possible," said Microsoft.
This month's Patch Tuesday, however, won't address two zero-day vulnerabilities which attackers are reportedly already actively exploiting.
On Tuesday, Microsoft confirmed a zero-day vulnerability that affects its graphics rendering engine, which an attacker could use to install programs, delete data, or create new user accounts. Microsoft also issued mitigation instructions, as well as a Fixit Button that home users and small businesses can use to mitigate the vulnerability.
Microsoft also released a suggested workaround for a zero-day CSS-related vulnerability that affects all versions of Internet Explorer. The flaw was recently disclosed by Google researcher Michal Zalewski, and later confirmed by French vulnerability research firm Vupen.
"The vulnerability exists due to the creation of uninitialized memory during a CSS function within Internet Explorer. It is possible under certain conditions for the memory to be leveraged by an attacker using a specially crafted Web page to gain remote code execution," said Microsoft.
According to Carlene Chmaj, senior response communications manager for Microsoft trustworthy computing, "we have started to see targeted attacks" using the CSS exploit.
Accordingly, beyond next week's Patch Tuesday, "there is also potential for further updates this month," said Qualys CTO Wolfgang Kandek."
Finally, there are two additional vulnerabilities currently being explored by security researchers. Both affect IE, and proof of concept attack code exists. "We expect Microsoft to acknowledge them soon," said Kandek.