A new attack, dubbed TunnelVision, has materialised as a threat to the security of virtual private network (VPN) applications, potentially compromising their ability to protect user data. Researchers have detected vulnerabilities affecting nearly all VPN apps, which could allow attackers to intercept, manipulate, or divert traffic outside of the encrypted tunnel, undermining the fundamental purpose of VPNs.
How TunnelVision Works
TunnelVision exploits a flaw in the Dynamic Host Configuration Protocol (DHCP) server, the system responsible for assigning IP addresses on a network. By manipulating a specific setting called option 121, attackers can divert VPN traffic through the DHCP server, bypassing the encrypted tunnel meant to secure the data. This manipulation allows attackers to intercept, read, drop, or modify the traffic, compromising the user's privacy and the integrity of the VPN connection.
Implications for VPN Users
The consequences of TunnelVision are severe. Despite users trusting that their data is securely transmitted through the VPN, the reality is that some or all of the traffic may be routed outside of the protected connection. This means that sensitive information, such as passwords, financial details, or personal communications, could be exposed to interception or manipulation by unauthorized parties.
The vulnerability affects a wide range of operating systems and devices, with the exception of Android, which does not implement option 121 in its DHCP server. For other operating systems, including Linux, there are no complete fixes available. Even with mitigations in place, such as minimising the effects on Linux, TunnelVision can still exploit side channels to compromise security.
While there is no foolproof solution to the TunnelVision attack, certain measures can reduce the risk. Running the VPN inside a virtual machine or connecting through a cellular device's Wi-Fi network can enhance security by isolating the VPN connection from potential attacks. However, these solutions may not be accessible or practical for all users, highlighting the need for further research and development in VPN security.
TunnelVision represents a harrowing threat to the integrity of VPNs, undermining their ability to protect user data from interception and manipulation. With the potential for widespread exploitation, it is essential for VPN providers and users to be aware of the risks and take appropriate measures to steer clear of potential attacks.
