Man-in-the-Middle (MitM) attack in Fortinet, Inc products - CVE-2024-3661

Description

The vulnerability allows a remote attacker to perform MitM attack.

The vulnerability exists due to way the VPN client handles routes advertised by the DHCP server. A remote attacker with access to the local network can route the victim's traffic to a malicious server instead of sending it via a secured channel. 

This vulnerability was dubbed "TunnelVision".

Remediation

External links

• https://datatracker.ietf.org/doc/html/rfc2131#section-7
• https://datatracker.ietf.org/doc/html/rfc3442#section-7
• https://tunnelvisionbug.com/
• https://www.leviathansecurity.com/research/tunnelvision
• https://news.ycombinator.com/item?id=40279632
• https://arstechnica.com/security/2024/05/novel-attack-against-virtually-all-vpn-apps-neuters-their-entire-purpose/
• https://krebsonsecurity.com/2024/05/why-your-vpn-may-not-be-as-secure-as-it-claims/
• https://issuetracker.google.com/issues/263721377
• https://mullvad.net/en/blog/evaluating-the-impact-of-tunnelvision
• https://www.zscaler.com/blogs/security-research/cve-2024-3661-k-tunnelvision-exposes-vpn-bypass-vulnerability
• https://lowendtalk.com/discussion/188857/a-rogue-dhcp-server-within-your-network-can-and-will-hijack-your-vpn-traffic
• https://news.ycombinator.com/item?id=40284111
• https://www.agwa.name/blog/post/hardening_openvpn_for_def_con
• https://www.theregister.com/2024/05/07/vpn_tunnelvision_dhcp/
• https://www.fortiguard.com/psirt/FG-IR-24-170