Multiple vulnerabilities have been reported in Internet Explorer, which can be exploited by malicious people to compromise a user's system.

1) A use-after-free error when processing Cascading Style Sheets (CSS) can be exploited to dereference freed memory via e.g. a specially crafted CSS file containing multiple import rules.

NOTE: According to Microsoft, the vulnerability is being actively exploited.

2) A use-after-free error when a certain data binding event removes a DSO (data source object) from the markup can be exploited to dereference already freed memory via a specially crafted web page.

3) An unspecified error exists in the way a certain object, which has not been correctly initialised or has been deleted, is accessed. This can be exploited to corrupt memory via a specially crafted web page.

4) Certain libraries (e.g. IEShims.dll) are loaded in an unsafe manner, which can be exploited to load arbitrary libraries by tricking a user into e.g. opening a HTML file located on a remote WebDAV or SMB share.

Successful exploitation of the vulnerabilities allows execution of arbitrary code.

Solution
Apply patches.
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Provided and/or discovered by
1) sec yun
2) The vendor credits Yuki Chen, Trend Micro.
3) The vendor credits SkyLined, Google.
4) MantyCore

Changelog
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Original Advisory
MS11-003 (KB2482017):
http://www.microsoft.com/technet/security/Bulletin/MS11-003.mspx

WooYun:
http://www.wooyun.org/bugs/wooyun-2010-0885

Other references
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Technical Analysis
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Deep Links
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