New Attack Renders Virtually All VPN Apps Ineffective, Undermining Their Core Purpose

The researchers' discovery of an attack, named TunnelVision, poses a significant threat to the security of virtual private network (VPN) applications. This attack targets nearly all VPN applications, compelling them to route traffic outside of the encrypted tunnel intended to protect it from interception or manipulation.The fundamental purpose of VPNs is to establish an encrypted tunnel through which all incoming and outgoing Internet traffic flows, thereby safeguarding user data and concealing their IP address. However, TunnelVision undermines this security mechanism, rendering VPNs ineffective in protecting user privacy and security.

According to the researchers, TunnelVision can compromise VPNs when connected to a hostile network, potentially exposing sensitive user data to interception or tampering. They assert that there are no effective countermeasures to mitigate this attack, except in cases where the user's VPN operates on Linux or Android platforms.Furthermore, the researchers speculate that this attack technique may have existed since as early as 2002, suggesting that it could have been exploited by threat actors in the past without detection. This raises concerns about the potential widespread exploitation of TunnelVision and underscores the urgent need for robust security measures to safeguard VPN users from such vulnerabilities.

TunnelVision allows attackers to intercept, manipulate, or drop VPN traffic, compromising the integrity and confidentiality of the user's data. As a result of this attack, the victim's traffic is diverted from the encrypted VPN tunnel and routed through the attacker's network. This enables the attacker to read, modify, or discard the leaked traffic, potentially exposing sensitive information or disrupting communication.Despite the victim maintaining a connection to both the VPN and the Internet, the security provided by the VPN is effectively bypassed, leaving the user vulnerable to various forms of cyberattacks. The ability to intercept and tamper with VPN traffic undermines the primary purpose of VPNs, which is to provide a secure and private channel for transmitting data over untrusted networks.This demonstration underscores the severity of TunnelVision's impact, highlighting the urgent need for VPN providers to address this vulnerability and implement robust security measures to protect users from such attacks.

TunnelVision operates by exploiting the DHCP (Dynamic Host Configuration Protocol) server responsible for assigning IP addresses to devices attempting to join the local network. Specifically, it leverages a configuration setting called option 121, which grants the DHCP server the authority to modify default routing instructions. Normally, VPN traffic is directed through a local IP address that establishes the secure tunnel. However, by manipulating option 121, the attack reroutes VPN data through the DHCP server, effectively directing it to the attacker's control. Researchers from Leviathan Security provided insights into this technique, shedding light on the mechanics behind Tunnel Vision's operation.