Zero-Day Advisory

Fortinet Discovers Resilio Sync DLL PreLoading Vulnerability

Summary

Fortinet's FortiGuard Labs has discovered a DLL preloading vulnerability in Resilio Sync for Windows.

Resilio Sync is a proprietary peer-to-peer file synchronization tool available for Windows, Mac, Linux, Android, iOS, Windows Phone, Amazon Kindle Fire and BSD. It can sync files between devices on a local network, or between remote devices over the Internet via a modified version of the BitTorrent protocol.

Resilio Sync for Windows is susceptible to a DLL preloading vulnerability. The issue occurs when the application looks to load a DLL for execution and an attacker provides a malicious DLL to use instead. The application generally follows a specific search path to locate the DLL. The vulnerability can be exploited by a simple file write (or potentially an over-write) which results in a foreign DLL running under the context of the application.

Solutions

Users should apply the solution provided by Resilio.

Timeline

Fortinet reported the vulnerability to Resilio on May 17, 2018.

Resilio confirmed the vulnerability on May 23, 2018.

Resilio released patch for it on May 23, 2018.

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.