SAS CTF and the many ways to persist a kernel shellcode on Windows 7

SAS CTF and the many ways to persist a kernel shellcode on Windows 7

On May 18, 2024, Kaspersky’s Global Research & Analysis Team (GReAT), with the help of its partners, held the qualifying stage of the SAS CTF, an international competition of cybersecurity experts held as part of the Security Analyst Summit conference. More than 800 teams from all over the world took part in the event, solving challenges based on real cases that Kaspersky GReAT encountered in its work, but a couple of challenges remained unsolved. One of those challenges was based on a security issue that allows kernel shellcode to be hidden in the system registry and executed during system boot on a fully updated Windows 7/Windows Server 2008 R2 due to an incomplete fix for the CVE-2010-4398 vulnerability. Although security updates and technical support for Windows 7 ended in early 2020, the fact that the released patch only partially addressed the issue was known long before that, and we saw this flaw exploited in a targeted attack in 2018. At the time, we notified Microsoft about the in-the-wild exploitation, but Microsoft refused to address it because using this technique requires attackers to have administrator privileges. In this blog post, we will provide technical details about this flaw and the SAS CTF task based on it.



Vulnerability details


There is a design flaw in older versions of Windows operating systems (Windows NT 4.0 through Windows 7) that allows a kernel shellcode to persist and be launched at system boot by writing specially crafted da ..

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