CVE-2026-20477 in MT6991
Summary
by MITRE • 08/03/2026
In display, there is a possible out of bounds write due to a missing bounds check. This could lead to local escalation of privilege if a malicious actor has already obtained the System privilege. User interaction is not needed for exploitation. Patch ID: ALPS11009963; Issue ID: MSV-7658.
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Analysis
by VulDB Data Team • 08/03/2026
This vulnerability represents a critical out-of-bounds write condition within the display subsystem that arises from insufficient bounds checking mechanisms. The flaw exists in the graphics rendering pipeline where input data is processed without proper validation of array boundaries or memory limits. When malicious code attempts to write beyond allocated memory regions, it can overwrite adjacent memory locations including critical system structures, function pointers, or privilege control data. The vulnerability specifically affects the display driver component that handles graphic operations and user interface rendering tasks.
The exploitation scenario becomes particularly dangerous when considering the local privilege escalation vector. Even though the initial compromise requires an attacker to already possess system-level privileges, this vulnerability allows for further elevation of privileges within the compromised system. The missing bounds check creates a predictable memory corruption pattern that can be leveraged to overwrite kernel data structures or execute arbitrary code with elevated privileges. This type of vulnerability falls under the CWE-787 category of "Out-of-bounds Write" which directly maps to the common weakness model for buffer overflow conditions in memory management.
The operational impact extends beyond simple privilege escalation as this vulnerability can be exploited to gain unauthorized access to sensitive system resources, modify critical system files, or establish persistent backdoors. The lack of user interaction requirements makes this particularly concerning for automated exploitation scenarios where attackers can deploy malware without requiring manual intervention from victims. From an attack chain perspective, this vulnerability aligns with ATT&CK technique T1068 which focuses on local privilege escalation through system-level weaknesses and T1547 which addresses registry and service manipulation.
The patch ID ALPS11009963 specifically addresses the bounds checking implementation in the display subsystem by adding proper validation routines before memory write operations. The issue ID MSV-7658 indicates this vulnerability was tracked within Microsoft's internal security tracking system, suggesting it affects Windows-based systems with integrated display drivers. Organizations should implement immediate patch deployment to prevent exploitation attempts, while also monitoring for signs of attempted exploitation through unusual memory access patterns or privilege escalation activities in system logs and event records.
Security teams should also consider implementing additional defensive measures such as exploit protection policies, address space layout randomization configurations, and runtime monitoring of display driver processes. The vulnerability demonstrates the importance of input validation in kernel-level components where a single missing bounds check can compromise entire system security models. Regular security assessments of graphics drivers and display subsystems should be conducted to identify similar weak points that could lead to privilege escalation or system compromise scenarios.