Zero-Day Advisory

Fortinet Discovers Microsoft Office Word Double Free Vulnerability

Summary

Fortinet's FortiGuard Labs has discovered a double free vulnerability in Microsoft Office 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.
A double free vulnerability was discovered in Microsoft Word when it fails to validate that a pointer was already released before attempting to release it again, causing conditions that attackers could leverage to achieve remote code execution scenarios. The underlying problem involves an internal structure that gets released without resetting the address to NULL. This causes Excel to release the pointer twice on certain resource consumption cases when it is running out of memory.

Solutions

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

MS.Office.WWLIB.Pointer.Handling.Memory.Corruption
Released Nov 30, 2015

Users should apply the solution provided by Microsoft.

Acknowledgement

This vulnerability was discovered by Kai Lu 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.