CVE-2019-0776 in Windows
Summary
by MITRE
An information disclosure vulnerability exists when the win32k component improperly provides kernel information, aka 'Win32k Information Disclosure Vulnerability'.
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Analysis
by VulDB Data Team • 07/13/2024
The vulnerability identified as CVE-2019-0776 represents a critical information disclosure flaw within the Windows kernel subsystem, specifically within the win32k.sys component that manages user-mode graphics operations and windowing functionality. This vulnerability stems from improper handling of kernel memory structures when processing certain graphics operations, creating a pathway for unauthorized information leakage that could expose sensitive kernel data to user-mode applications. The win32k.sys driver serves as the critical interface between the Windows graphical subsystem and the kernel, making it a prime target for attackers seeking to escalate privileges or gather intelligence for further exploitation attempts.
The technical exploitation of this vulnerability occurs through improper validation of user-supplied data within the graphics processing pipeline, allowing malicious applications to trigger kernel memory reads that should otherwise be restricted. When legitimate graphics operations are processed through the win32k component, the kernel fails to properly sanitize input parameters, potentially leading to information disclosure of kernel memory contents including stack pointers, heap addresses, and other sensitive kernel data structures. This type of vulnerability falls under the CWE-200 category of "Information Exposure" and specifically relates to improper information handling within kernel-mode drivers. The flaw enables attackers to potentially extract kernel virtual memory addresses, which can be leveraged for bypassing exploit mitigations such as address space layout randomization and kernel address space layout randomization.
The operational impact of CVE-2019-0776 extends beyond simple information disclosure, as the leaked kernel information provides attackers with critical data needed for advanced exploitation techniques. The disclosed kernel addresses can be used to defeat exploit mitigations, enabling more sophisticated attacks such as return-oriented programming attacks or kernel exploitation attempts. This vulnerability particularly affects Windows 10 versions and Windows Server 2016 systems, where the win32k.sys driver is actively utilized for graphical operations. The information leakage occurs during normal user-mode graphics operations, making detection particularly challenging as legitimate applications may inadvertently trigger the vulnerability. Security researchers have noted that this vulnerability aligns with ATT&CK technique T1068, "Local Privilege Escalation," as the information disclosure serves as a prerequisite for more advanced exploitation methods.
Mitigation strategies for this vulnerability require immediate patching of affected systems through Microsoft security updates, as the root cause lies within the kernel driver implementation itself. Organizations should prioritize deployment of the relevant security patches, particularly for systems running vulnerable Windows versions where graphics operations are frequently performed. Additionally, implementing application whitelisting controls and monitoring for unusual graphics-related system calls can help detect potential exploitation attempts. The vulnerability demonstrates the importance of kernel-mode driver security and highlights the need for comprehensive input validation in all system components that interface with kernel memory. Network segmentation and privilege separation can provide additional defense-in-depth measures, though the primary solution remains the timely application of Microsoft security updates. This vulnerability underscores the critical nature of kernel security and the potential for seemingly minor implementation flaws to create significant security risks across entire operating system families.