Zero-Day Advisory

Fortinet Discovers Microsoft Word RTF File Handling Memory Corruption Vulnerability

Summary

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

Microsoft Office is an office suite of applications, servers and services. It was first announced by Microsoft in 1988. The first version of Office contained Microsoft Word, Microsoft Excel and Microsoft PowerPoint. Over the years, Office applications have grown substantially closer with shared features such as a common spell checker, OLE data integration and Visual Basic for Applications scripting language. Microsoft also positions Office as a development platform for line-of-business software under the Office Business Applications brand.

The memory corruption vulnerability is caused by an object type confusion. It exists because Microsoft Word improperly handles a specially crafted Rich Text File (RTF) document. The vulnerability can be triggered when bogus "listoverride" control word is used within 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.


Solutions

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

MS.Office.RTF.Listoverride.File.Handling.Memory.Corruption
Released Mar 13, 2018

Users should apply the solution provided by Microsoft.

Timeline

Fortinet reported the vulnerability to Microsoft on December 28, 2017.

Microsoft confirmed the vulnerability on January 12, 2018.

Microsoft patched the vulnerability on March 13, 2018.

Acknowledgement

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.