Zero-Day Advisory

Fortinet Discovers Microsoft Word RTF File Handling Memory Corruption Vulnerability


Fortinet's FortiGuard Labs has discovered a memory corruption vulnerability in Microsoft Word.

Microsoft Word is a word processor developed by Microsoft and it is one of the components of Microsoft Office suites.

The memory corruption vulnerability is caused by an Use-After-Free error. It exists because Microsoft Word improperly handles a specially crafted Rich Text File (RTF) document. The vulnerability can be triggered when bogus style sheet is used in the RTF document. As a result, it can lead to arbitrary code execution upon successful exploitation when the crafted document is opened using the vulnerable Microsoft Word.


FortiGuard Labs released the following FortiGate IPS signature which covers this specific vulnerability:

Released Jan 05, 2018

Users should apply the solution provided by Microsoft.

Additional Information

Fortinet reported the vulnerability to Microsoft on November 14, 2017.

Microsoft confirmed the vulnerability on December 12, 2017.

Microsoft patched the vulnerability on January 09, 2018.


This vulnerability was discovered by Wayne Low of Fortinet's FortiGuard Labs.

IPS Subscription

Fortinet customers who subscribe to Fortinet's intrusion prevention (IPS) service should be protected against this vulnerability with the appropriate configuration parameters in place. Fortinet's IPS service is one component of FortiGuard Subscription Services, which also offer comprehensive solutions such as antivirus, Web content filtering and antispam capabilities. These services enable protection against threats on both application and network layers. FortiGuard Services are continuously updated by FortiGuard Labs, which enables Fortinet to deliver a combination of multi-layered security intelligence and true zero-day protection from new and emerging threats. These updates are delivered to all FortiGate, FortiMail and FortiClient products. Fortinet strictly follows responsible disclosure guidelines to ensure optimum protection during a threat's lifecycle.