Zero-Day Advisory

Fortinet Discovers Windows SharedAccess Denail-of-service Vulnerability


Fortinet's FortiGuard Labs has discovered a Denial-of-Service (DoS) vulnerability on Microsoft Windows SharedAccess service.

Microsoft Windows SharedAccess is also known as Internet Connection Sharing (ICS). It provides network address translation, addressing, name resolution and/or intrusion prevention services for a home or small office network.

The DoS vulnerability can occur when a DHCP request contains the DHCP message type DHCP_MESSAGE_DECLINE while there is no valid DHCP_OPTION_REQUESTEDIPADDR embedded in the same DHCP request.


Users should apply the solution provided by Microsoft.


Fortinet reported the vulnerability to Microsoft on September 15, 2022

Microsoft confirmed the vulnerability on September 23, 2022

Microsoft released a patch for the vulnerability on December 13, 2022


This vulnerability was discovered by Wayne Low 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.