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.