CVE-2018-8120

CVE-2018-8120 is an elevation of privilege flaw in the Microsoft Windows Win32k kernel component, which fails to properly handle objects in memory. A local attacker who already has the ability to run code with low privileges on the machine must execute a specially crafted application that triggers the faulty object handling, allowing code to run in kernel mode. Successful exploitation yields elevated (SYSTEM-level) privileges and full control of the host, and it is commonly chained with a remote code execution or browser exploit, or used by malware — including ransomware — to deepen a compromise. Only systems running Windows 7, Windows Server 2008, or Windows Server 2008 R2 with unpatched Win32k are affected. The bug was exploited as a zero-day (reportedly by the ScarCruft APT group) before being fixed in May 2018 Patch Tuesday, a public PoC is available, and it was added to CISA's Known Exploited Vulnerabilities catalog in March 2022 with known ransomware use.

What to do: Apply Microsoft's May 2018 security updates or later cumulative updates for Windows 7, Windows Server 2008, and Windows Server 2008 R2, prioritizing this KEV-listed flaw per the CISA required action. Systems beyond end of support that are not receiving Extended Security Updates should be migrated to a supported Windows version or isolated, since they remain permanently exposed to known APT and ransomware tooling. Review hosts for signs of local privilege escalation and ensure any RCE entry vector (browser, file format, or service exploit) is also patched, as this bug is typically used to escalate an initial foothold.