Zero-Day Advisory

Fortinet Discovers Google Chrome Skia Engine Heap Overflow Vulnerability

Summary

Fortinet's FortiGuard Labs has discovered a heap overflow vulnerability in Google Chrome Skia engine.
Skia is an open source 2D graphics library which provides common APIs that work across a variety of hardware and software platforms. It serves as the graphics engine for Google Chrome and Chrome OS, Android, Mozilla Firefox and Firefox OS, and many other products. The Skia image rendering engine contains several Effect Filters which can be applied to an pre-existing sourced Bitmap Image or to a new Skia Drawing.
The heap overflow vulnerability is caused due to an incorrect bounds check in SkRegionPriv whilst implementing the Skia Filter SkAlphaThresholdFilter. The malformed data supplied to the SkAlphaThresholdFilter filter escapes the bounds set in SkRegionPriv which leads to a heap-based buffer overflow. Thus this vulnerability can be triggered by loading a malicious webpage wherein malformed input data is provided to the Skia SkAlphaThresholdFilter Effect Filter, thereby causing the Skia rendering engine to crash.


Solutions

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

Chrome.Skia.Heap.Overflow
Released Mar 14, 2017

Users should apply the solution provided by Google.

Additional Information

Chrome version 57.0.2987.87 and before are affected.

Acknowledgement

This vulnerability was discovered by Kushal Arvind Shah 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.