CVE-2018-8406

What is the DirectX Graphics Kernel?

The DirectX Graphics Kernel driver (dxgkrnl.sys) is the kernel-mode component of the Windows graphics stack, mediating between user-mode graphics calls and the GPU. As with other kernel-mode drivers reachable from user mode, memory-handling bugs here are a frequent source of local privilege-escalation vulnerabilities.

Overview

CVE-2018-8406 is an elevation of privilege vulnerability in DXGKRNL caused by improper handling of objects in memory, patched by Microsoft in the same August 2018 update cycle as the closely related CVE-2018-8405. A locally authenticated attacker who runs a specially crafted application can exploit the flaw to execute code in kernel mode and escalate to SYSTEM privileges.

Technical Details

Like its sibling CVE-2018-8405, this bug falls under CWE-404 (Improper Resource Shutdown or Release): DXGKRNL mishandles a kernel object's lifecycle in a way that a local, low-privileged caller can trigger and exploit to corrupt kernel memory. Microsoft assigned it a distinct CVE because it represents a separately identified code path within the same driver rather than a duplicate report of the same bug.

Discovery

The issue was addressed through Microsoft's regular security update process as part of the August 2018 Patch Tuesday release.

Exploitation Context

CISA added CVE-2018-8406 to the KEV catalog in March 2022, and the entry notes confirmed use in ransomware operations, consistent with the pattern of kernel EoP bugs being used as a second stage after initial compromise to obtain the elevated privileges needed for mass file encryption or credential dumping.

Remediation

1. Apply the August 2018 Windows security update (or later cumulative update), which addresses this vulnerability alongside CVE-2018-8405.
2. Treat DXGKRNL patches as high priority on multi-user or shared systems where local code execution by lower-privileged users is more likely.
3. Apply least-privilege and application allowlisting controls to reduce the chance of an attacker reaching this local-only attack surface in the first place.
4. Keep EDR and kernel-level monitoring active to detect anomalous privilege-escalation behavior.
5. Include graphics/kernel driver updates in routine patch management alongside standard OS security updates.