BranchCache is a wide area network (WAN) bandwidth optimization technology (included in some editions of the Windows Server 2008 R2 and Windows 7 operating systems) that allows content from file and Web servers on a wide area network (WAN) to be cached on computers locally
When the default DLL does exist on the system, this binary will be searched for first in safe, local locations in the Windows folder structure and when not found , the application will attempt to locate the file on the location from where the file is opened, which could be an insecure location such as a network share.
This can be exploited to load an arbitrary library by tricking a user into e.g. opening .eml and .rss (Windows Live Mail) or .wpost (Microsoft Live Writer) files located on a remote WebDAV or SMB share.
- Disable loading of libraries from WebDAV and remote network.
- Disable the WebClient service.
- Block TCP ports 139 and 445 at the firewall.
For detailed steps and impact of applying these workarounds refer to Microsoft Security Bulletin MS10-095
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