DHCP routing options can manipulate interface-based VPN traffic

Vulnerability Description

DHCP can add routes to a client’s routing table via the classless static route option (121). VPN-based security solutions that rely on routes to redirect traffic can be forced to leak traffic over the physical interface. An attacker on the same local network can read, disrupt, or possibly modify network traffic that was expected to be protected by the VPN.

References

• 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://support.citrix.com/article/CTX677069/cloud-software-group-security-advisory-for-cve20243661
• https://www.watchguard.com/wgrd-psirt/advisory/wgsa-2024-00009
• https://bst.cisco.com/quickview/bug/CSCwk05814
• https://security.paloaltonetworks.com/CVE-2024-3661
• https://fortiguard.fortinet.com/psirt/FG-IR-24-170
• https://my.f5.com/manage/s/article/K000139553