CVE-2023-20684 in MT6789
Summary
by MITRE • 04/06/2023
In vdec, there is a possible use after free 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: ALPS07671069; Issue ID: ALPS07671069.
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Analysis
by VulDB Data Team • 08/31/2025
The vulnerability identified as CVE-2023-20684 resides within the video decoder component known as vdec, representing a critical security flaw that could enable local privilege escalation. This issue stems from a race condition that creates a window of opportunity for malicious exploitation, allowing an attacker with system execution privileges to potentially elevate their access level. The vulnerability specifically manifests as a use-after-free condition, where memory that has been deallocated is still being referenced, creating potential for arbitrary code execution or system compromise. The absence of user interaction requirements for exploitation makes this particularly concerning as it can be triggered automatically without any deliberate action from the end user.
The technical implementation of this flaw occurs within the vdec subsystem where concurrent processes or threads access shared memory resources without proper synchronization mechanisms. This race condition allows for a timing window where one thread deallocates memory while another thread attempts to access the same memory location, resulting in the use-after-free scenario. The vulnerability is classified under CWE-416 as a use-after-free condition, which is a well-documented class of memory safety issues that frequently leads to privilege escalation attacks. The attack vector specifically targets the video decoding process where multiple threads may be operating simultaneously, creating the necessary conditions for the race condition to occur.
The operational impact of this vulnerability extends beyond simple privilege escalation as it represents a significant threat to system integrity and security posture. An attacker who successfully exploits this vulnerability can gain elevated system privileges, potentially allowing them to access sensitive data, modify system configurations, or establish persistent access to the compromised system. The local nature of the exploit means that the attacker must already have some level of system execution capability, but the privilege escalation aspect makes the attack particularly dangerous. This vulnerability aligns with ATT&CK technique T1068 which covers 'Local Privilege Escalation' and specifically addresses scenarios where race conditions in kernel or system components can be exploited to gain higher privileges.
Mitigation strategies for CVE-2023-20684 should focus on implementing proper synchronization mechanisms within the vdec subsystem to prevent race conditions from occurring. The patch ALPS07671069 addresses this issue by introducing appropriate locking mechanisms and memory management controls that eliminate the timing window where the race condition could be exploited. System administrators should prioritize applying this patch immediately, as the vulnerability does not require user interaction for exploitation. Additional defensive measures include implementing memory safety checks, monitoring for unusual memory access patterns, and conducting regular security assessments of system components. Organizations should also consider implementing process isolation and privilege separation techniques to limit the potential impact if such vulnerabilities are exploited in the future. The fix demonstrates the importance of proper concurrent programming practices and highlights the critical need for thorough testing of multi-threaded system components to prevent similar race condition vulnerabilities from emerging in other system areas.