Zero-Day Advisory

Fortinet Discovers Windows Font Library Memory Corruption Vulnerability

Summary

Fortinet's FortiGuard Labs has discovered a Memory Corruption vulnerability in Microsoft Windows Embedded OpenType font library.

The EOT font library allows compressed OpenType font to be embedded in various font formats. The vulnerable Windows font library is used by many applications ranging from Internet Explorer, Microsoft Office and other third party software that utilizes this font library. The font library exists in all version of Windows.

The Memory Corruption vulnerability exists when the Windows font library improperly handles specially crafted embedded fonts. An attacker who successfully exploited this vulnerability would gain code execution on the target system.

Solutions

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

MS.Windows.Express.Compressed.Fonts.Remote.Code.Execution
Released Aug 17, 2017

Users should apply the solution provided by Microsoft.

Timeline

Fortinet reported the vulnerability to Microsoft on July 29, 2017.

Microsoft patched the vulnerability on August 8, 2017.

References

• https://portal.msrc.microsoft.com/en-us/security-guidance/advisory/CVE-2017-8691
  

• CVE-2017-8691

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.