A vulnerability in the network stack of Cisco NX-OS Software could allow an unauthenticated, remote attacker to bypass certain security boundaries or cause a denial of service (DoS) condition on an affected device. The vulnerability is due to the affected device unexpectedly decapsulating and processing IP in IP packets that are destined to a locally configured IP address. An attacker could exploit this vulnerability by sending a crafted IP in IP packet to an affected device. A successful exploit could cause the affected device to unexpectedly decapsulate the IP in IP packet and forward the inner IP packet. This may result in IP packets bypassing input access control lists (ACLs) configured on the affected device or other security boundaries defined elsewhere in the network. Under certain conditions, an exploit could cause the network stack process to crash and restart multiple times, leading to a reload of the affected device and a DoS condition. Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability. This advisory is available at the following link: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-ipip-dos-kCT9X4 ["https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-ipip-dos-kCT9X4"]

IP-in-IP protocol specifies IP Encapsulation within IP standard (RFC 2003, STD 1) that decapsulate and route IP-in-IP traffic is vulnerable to spoofing, access-control bypass and other unexpected behavior due to the lack of validation to verify network packets before decapsulation and routing.

Multiple products that implement the IP Encapsulation within IP standard (RFC 2003, STD 1) decapsulate and route IP-in-IP traffic without any validation, which could allow an unauthenticated remote attacker to route arbitrary traffic via an exposed network interface and lead to spoofing, access control bypass, and other unexpected network behaviors.