Microsoft has warned its Word software is vulnerable to a newly discovered dangerous bug – which is being exploited right now in "limited, targeted attacks" in the wild. There is no patch available at this time.
The flaw is triggered by opening a maliciously crafted RTF document in the Microsoft Office word processor, or opening it via Outlook, and allows the attacker to execute arbitrary code on the machine.
The hole was disclosed by Microsoft on Monday outside the monthly Patch Tuesday cycle. Opening a poisoned Rich Text File (RTF) document allows the attacker to hijack the PC with the same privileges as the logged-in user.
Microsoft Word 2003, 2007, 2010, 2013, and Office for Mac 2011 are vulnerable, according to Redmond. Microsoft Office Web Apps, Automation Services on SharePoint Server 2010 and 20103, and Outlook 2007, 2010 and 2013 when using Word as the email viewer, are also affected.
Drew Hintz, Shane Huntley, and Matty Pellegrino of the Google Security Team reported the Word RTF memory-corruption flaw to Microsoft; the bug was assigned CVE-2014-1761 on January 31.
One particularly nasty part of the flaw is that it can be triggered if a specially crafted RTF document attached to an email is previewed in Outlook. Alternatively, "an attacker could host a website that contains a webpage that contains a specially crafted RTF file that is used to attempt to exploit this vulnerability," Microsoft explained.
"An attacker who successfully exploited the vulnerability could gain the same user rights as the current user. If the current user is logged on with administrative user rights, an attacker who successfully exploited this vulnerability could take complete control of an affected system."
Microsoft says admins should disable the opening of RTF data in Microsoft Word to prevent exploitation of the vulnerability. Using the Enhanced Mitigation Experience Toolkit may also thwart attempts to compromise systems via this hole.
"On completion of investigation for this vulnerability, Microsoft will take the appropriate action to protect our customers, which may include providing a solution through our monthly security update release process, or an out-of-cycle security update, depending on customer needs," the corporation added. ®