Software Engineering Institute

From Murray Sargent's MSDN blog:

RichEdit 6.0 is a facility for getting plain/rich-text, single/multiline Unicode/ANSI edit controls and combo/list boxes in single world-wide binary that runs on all Windows operating systems.

A remote code execution vulnerability exists in the RichEdit components that are shipped with Microsoft Windows and Microsoft Office. An attacker may be able to exploit this vulnerability by convincing a user to open a specially crafted Rich Text Format (RTF) file that includes an embedded malformed OLE object.

Note that Microsoft states that to exploit this vulnerability an attacker would need to persuade a user to open a malicious file or an email attachment.

A remote unauthenticated attacker may be able to execute arbitrary code with the privileges of the user who is running the vulnerable application.

Update
Microsoft has released an update to address this issue. See Microsoft Security Bulletin MS07-013 for more details.

Do not allow WordPad to parse embedded files

Microsoft WordPad is the default application for opening and interacting with RTF files in Microsoft Windows. Preventing WordPad from parsing embedded OLE objects in RTF files may mitigate this vulnerability. See the workarounds section of Microsoft Security Bulletin MS07-013 for instructions on how to edit the Windows registry to prevent WordPad from parsing these objects.

Do not run Windows with administrator privileges

Running Windows using an unprivileged regular user account may mitigate the affects of this vulnerability. See the Microsoft Technet article Applying the Principle of Least Privilege to User Accounts on Windows XP for more information.