IPv4-in-IPv6 and IPv6-in-IPv6 Tunneling Vulnerability Allowing Traffic Spoofing and Routing

A vulnerability exists in IPv4-in-IPv6 and IPv6-in-IPv6 tunneling protocols, as defined in RFC 2473, due to the lack of source packet validation. This flaw enables an attacker to spoof and route arbitrary traffic through a vulnerable host's network interface. The issue arises from the protocols' inherent design, which does not authenticate or encrypt traffic, leaving them open to exploitation. This vulnerability is particularly concerning because it can be used to bypass network filters and conduct anonymous attacks, similar to a previously identified vulnerability in IP-in-IP tunneling (CVE-2020-10136).

Impact

Exploitation of this vulnerability allows for traffic spoofing, where an attacker can send packets that appear to come from a trusted source, bypassing network security measures. This can lead to unauthorized access to private networks, where internal resources such as security cameras or home automation systems could be compromised. Additionally, the vulnerability can be exploited to perform denial-of-service attacks, including two new amplification attacks that significantly increase the volume of traffic directed at a target.

Reproduction

The vulnerability can be reproduced by sending a tunneling packet with a spoofed source address from an unverified source. The vulnerable host will decapsulate the packet and forward the inner packet without authenticating the sender, effectively routing the spoofed traffic to the intended destination. This can be done manually or automated with a script.

Remediation

To address this vulnerability, hosts should be configured to accept tunneling packets only from trusted sources. Additionally, using more secure tunneling protocols that include authentication and encryption, such as IPsec or WireGuard, is recommended. ISPs and network owners can also implement traffic filtering on routers to block unencrypted tunneling packets from entering or leaving the network.