Technical Tip: Mitigation Measures for FG-IR-24-219 Vulnerability Without Firmware Upgrade

The recommended solution to mitigate FG-IR-24-219 is to upgrade to an unaffected firmware version, as outlined in the official Fortinet advisory: Multipart Form Data Denial of Service.

However, if upgrading is not an immediate option, the following mitigation measures can help reduce the risk:

• Mitigation Steps:
  This vulnerability is exploitable only if an attacker has access to the HTTP or HTTPS management interface of the firewall.
• The most effective measure is to disable HTTPS and HTTP administrative access (Technical Tip: System administrator best practices for FortiGate and FortiProxy) on external interfaces to prevent unauthorized access. 
• If remote management is required, implement a local-in policy to restrict HTTP/HTTPS (Technical Tip: Impact of Local-In Policies and Trusted Hosts Configuration on FortiGate Access) access only to trusted IP addresses.
• The trust host configuration is validated after the entire HTTP request is received, which may be insufficient as a primary mitigation method.

Limitations of the Workaround:

• These steps help reduce the likelihood of exploitation but do not eliminate the vulnerability.
• The only definitive solution is to upgrade to an unaffected firmware version.