NatJack Attack: Exploiting NAT Vulnerabilities in Windows and Linux
In August 2026, security researcher Malcolm Stagg unveiled 'NatJack,' a novel attack class that exploits vulnerabilities in Network Address Translation (NAT) implementations to hijack active TCP sessions, spoof DNS responses, expose mapped ports, and exhaust NAT tables. The research identified two critical vulnerabilities: CVE-2026-56181 in Windows NAT used by Hyper-V and CVE-2026-63913 in Linux Netfilter conntrack. These flaws allow attackers with privileged access to a system behind the same NAT as the victim to manipulate connection states, leading to potential data interception and service disruptions. Organizations are advised to apply the latest patches and implement network segmentation to mitigate these risks. The NatJack disclosure underscores the evolving threat landscape targeting network infrastructure. As attackers continue to find and exploit design assumptions in widely used technologies, it is imperative for organizations to reassess their network security postures, prioritize internal traffic encryption, and adopt zero-trust principles to safeguard against such sophisticated attacks.
Kill Chain
