Zero-Day Advisory

Fortinet Discovers Symantec Norton Utilities DLL Preloading Vulnerability


Fortinet's FortiGuard Labs has discovered a DLL preloading vulnerability in Symantec Norton Utilities.

Norton Utilities is a small but very efficient software that was specifically designed to help analyze, configure, optimize and maintain a computer. It cleans and speeds up the PC by fixing common issues that can cause slowdowns or crashes, frees up space on your hard drive, by finding duplicate files and unused applications that can be discarded, safely disposes of personal documents and also helps maintain digital privacy by erasing recently opened files and website browsing history, recovers photos, documents, and other files that may have been damaged or accidentally deleted.

Norton Utilities 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.


Users should apply the solution provided by Symantec.


Fortinet reported the vulnerability to Symantec on August 06, 2017.

Symantec confirmed the vulnerability on May 22, 2018.

Symantec patched the vulnerability on August 22, 2018.


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.