CVE-2023-20736 in MT6768
Summary
by MITRE • 06/06/2023
In vcu, there is a possible out of bounds write due to a race condition. This could lead to local escalation of privilege with System execution privileges needed. User interaction is not needed for exploitation. Patch ID: ALPS07645149; Issue ID: ALPS07645189.
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Analysis
by VulDB Data Team • 01/08/2025
The vulnerability identified as CVE-2023-20736 represents a critical out-of-bounds write condition within the vcu component of a system, fundamentally compromising memory safety and potentially enabling privilege escalation. This flaw arises from a race condition that occurs during concurrent access to shared resources, creating a window where memory operations can exceed allocated boundaries. The vulnerability specifically affects systems where the vcu module handles multimedia processing or video decoding tasks, making it particularly concerning in environments where such components are extensively utilized.
The technical root cause of this vulnerability stems from improper synchronization mechanisms within the vcu subsystem, allowing multiple threads or processes to access and modify shared memory locations simultaneously. This race condition creates a scenario where one thread may attempt to write data beyond the bounds of a allocated memory buffer while another thread is simultaneously accessing or modifying the same memory region. The flaw manifests as an out-of-bounds write operation that can overwrite adjacent memory locations, potentially corrupting critical system data structures or executable code. This type of vulnerability is categorized under CWE-367 which specifically addresses Time-of-Check to Time-of-Use (TOCTOU) vulnerabilities and race conditions that can lead to memory corruption.
The operational impact of this vulnerability extends beyond simple memory corruption, as it provides a pathway for local privilege escalation to system execution privileges. An attacker who successfully exploits this vulnerability can leverage the out-of-bounds write to overwrite critical system components or function pointers, ultimately gaining elevated privileges within the operating system. The exploitation requires no user interaction, making it particularly dangerous as it can be triggered automatically by malicious processes or by exploiting other vulnerabilities within the system. This characteristic aligns with ATT&CK technique T1068 which focuses on exploiting vulnerabilities to gain system-level privileges without requiring user interaction.
The patch ID ALPS07645149 and issue ID ALPS07645189 indicate this vulnerability was identified within a specific firmware or kernel subsystem, likely related to Android-based operating systems or embedded systems where vcu components are commonly implemented. The vulnerability's exploitation potential makes it a high-priority target for threat actors seeking to establish persistent system-level access, particularly in environments where the affected system components are widely deployed. Organizations should implement immediate mitigation strategies including firmware updates, memory protection mechanisms, and process isolation techniques to prevent exploitation of this vulnerability.
Security practitioners should monitor for indicators of compromise related to this vulnerability, particularly unusual memory access patterns or privilege escalation attempts within system logs. The vulnerability's classification as a race condition makes it susceptible to various exploitation techniques including heap spraying or controlled memory corruption attacks. System administrators should also consider implementing additional security controls such as kernel address space layout randomization and stack canaries to further mitigate the impact of potential exploitation attempts. The vulnerability demonstrates the importance of proper synchronization mechanisms in concurrent programming environments and highlights the critical need for thorough testing of multi-threaded system components to prevent similar issues from occurring in the future.