Zero-Day Advisory

Fortinet Discovers Windows PE Signature Spoofing Vulnerability


Fortinet's FortiGuard Labs has discovered a vulnerability to bypass Windows PE Authenticode signature validation.

The Portable Executable (PE) format is a file format for executables, object code, DLLs and others used in Microsoft Windows operating systems. The PE format is a data structure that encapsulates the information necessary for the Windows OS loader to manage the wrapped executable code.

A bypass vulnerability has been discovered in Windows PE Authenticode signature validation. The vulnerability exists due to the signature computation mechanism. It could allow an attacker to disguise an altered executable as legitimate software.


Users should apply the solution provided by Microsoft.


Fortinet reported the vulnerability to Microsoft on June 24, 2021. 

Microsoft confirmed the vulnerability on June 29, 2021.

Microsoft patched the vulnerability on September 14, 2021.


This vulnerability was discovered by Udi Yavo and Asaf Rubinfeld 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.