Security Vulnerabilities in Tunneling Protocols Pose Serious Threats to Internet Infrastructure

 

Introduction
Recent research has revealed significant security flaws in various tunneling protocols, which could potentially allow attackers to exploit vulnerable internet infrastructure. These vulnerabilities have been identified across multiple devices, including VPN servers, routers, and content delivery network (CDN) nodes. The risks associated with these flaws are substantial, with the potential for attackers to perform anonymous attacks and disrupt essential services. This article explores the nature of these vulnerabilities, the protocols affected, and the recommended measures to mitigate potential threats.

Security Vulnerabilities and Impact
According to a study by Top10VPN, in collaboration with KU Leuven professor Mathy Vanhoef, internet hosts that accept tunneling packets without verifying the sender's identity are at risk. The lack of proper authentication and encryption in certain tunneling protocols makes these systems susceptible to various attacks, including denial-of-service (DoS) and distributed denial-of-service (DDoS) attacks. In total, up to 4.2 million hosts worldwide, including VPN servers, home routers, mobile network gateways, and core internet routers, are exposed to these vulnerabilities. Countries such as China, France, Japan, the U.S., and Brazil have been identified as having the most affected networks.

The exploited vulnerabilities enable attackers to create one-way proxies and spoof source IP addresses, allowing them to carry out attacks with a masked origin. By exploiting these weaknesses, adversaries can infiltrate private networks or use compromised systems for malicious purposes, including launching DDoS attacks.

Tunneling Protocols at Risk
The vulnerabilities are found in several tunneling protocols, including IP6IP6, GRE6, 4in6, and 6in4, which are used to facilitate data transfer between disconnected networks. The primary issue lies in the lack of encryption and authentication for traffic within these protocols. When the proper security protocols, like Internet Protocol Security (IPsec), are not implemented, it becomes easier for attackers to inject malicious traffic into these tunnels.

These security flaws were first noted in 2020 and have now been assigned the following CVE identifiers for further tracking:

• CVE-2024-7595 (GRE and GRE6)
• CVE-2024-7596 (Generic UDP Encapsulation)
• CVE-2025-23018 (IPv4-in-IPv6 and IPv6-in-IPv6)
• CVE-2025-23019 (IPv6-in-IPv4)

The vulnerability is described by Top10VPN's Simon Migliano, who explains that an attacker can exploit these flaws by sending a specially crafted packet. This packet has two IP headers: one that contains the attacker's source IP and the vulnerable host's IP as the destination, and another with the vulnerable host's IP as the source address. As the vulnerable system strips the outer header, the malicious packet is forwarded to its destination, bypassing network filters that rely on the trusted source IP.

Recommended Defenses
To counter these threats, several defense measures have been proposed. Firstly, the use of robust encryption and authentication protocols such as IPsec or WireGuard can help secure tunneling traffic. It is also essential for networks to only accept tunneling packets from trusted sources to reduce the risk of unauthorized access.

Additionally, network-level defenses are critical. These include traffic filtering on routers, implementing Deep Packet Inspection (DPI), and blocking unencrypted tunneling packets altogether. These measures can prevent attackers from injecting harmful traffic into the network and help mitigate the impact of DDoS attacks.

Conclusion
The recent discovery of security vulnerabilities in tunneling protocols highlights the critical need for enhanced security measures in internet infrastructure. Organizations and network administrators must prioritize the implementation of encryption protocols and rigorous traffic filtering to protect against exploitation. The risks associated with these vulnerabilities include network congestion, service disruptions, and potential data interception, making it essential to act quickly to secure vulnerable systems. By addressing these flaws, internet infrastructure can become more resilient to attacks, ensuring a safer digital environment for all users.