CVE-2018-8637 in Windows
Summary
by MITRE
An information disclosure vulnerability exists in Windows kernel that could allow an attacker to retrieve information that could lead to a Kernel Address Space Layout Randomization (KASLR) bypass, aka "Win32k Information Disclosure Vulnerability." This affects Windows 10 Servers, Windows 10, Windows Server 2019.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 06/18/2023
The vulnerability identified as CVE-2018-8637 represents a critical information disclosure flaw within the Windows kernel subsystem that specifically impacts the win32k.sys driver component. This vulnerability resides in the kernel-mode driver that handles graphics and user interface operations, making it particularly dangerous as it operates at the most privileged level of the operating system. The flaw allows unauthorized access to kernel memory addresses and system information that should remain protected from user-mode processes. This type of vulnerability falls under the Common Weakness Enumeration category CWE-200, which specifically addresses information exposure issues where sensitive data is unintentionally revealed to unauthorized parties.
The technical mechanism behind this vulnerability involves improper handling of certain kernel objects within the win32k.sys driver during specific graphics operations. When user-mode applications interact with the graphics subsystem through the Windows API, the kernel processes these requests and may inadvertently expose kernel memory addresses or other sensitive information through error handling mechanisms or object state information. The vulnerability specifically affects the KASLR bypass capability because the leaked information can reveal memory layout details that would otherwise be randomized to prevent exploitation. This information disclosure is particularly significant as KASLR is a primary defense mechanism against kernel exploits, and its bypass significantly increases the attack surface for sophisticated adversaries.
The operational impact of CVE-2018-8637 extends beyond simple information disclosure, as it creates a pathway for more advanced exploitation techniques. Attackers who successfully leverage this vulnerability can gain insights into kernel memory addresses, which enables them to craft more precise and effective kernel exploits. This vulnerability is particularly concerning in server environments where Windows 10 Servers and Windows Server 2019 are deployed, as these systems often handle sensitive data and critical operations. The attack surface is broadened because the vulnerability can be exploited through various attack vectors including malicious software installation, web browsing, or even physical access scenarios where an attacker can interact with the graphics subsystem. The vulnerability aligns with ATT&CK technique T1059 which involves executing malicious code through legitimate system processes, and T1068 which covers privilege escalation through kernel exploits.
Mitigation strategies for this vulnerability require immediate patch deployment from Microsoft as the primary defense mechanism. Organizations should prioritize patch management processes to ensure all affected Windows systems receive the security updates released by Microsoft to address this specific information disclosure flaw. Additionally, implementing network segmentation and access controls can limit the potential impact of exploitation attempts, while monitoring for unusual graphics subsystem activity can help detect potential exploitation attempts. The vulnerability demonstrates the critical importance of maintaining up-to-date security patches and the potential consequences of delayed remediation efforts. Security teams should also consider implementing kernel-mode protection mechanisms and monitoring for suspicious kernel address leaks that could indicate exploitation attempts. This vulnerability serves as a reminder of the critical need for comprehensive security testing and the potential risks associated with kernel-level flaws that can undermine fundamental security protections like KASLR.