CVE-2023-20685 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: ALPS07608575; Issue ID: ALPS07608575.
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Analysis
by VulDB Data Team • 08/31/2025
The vulnerability identified as CVE-2023-20685 resides within the video decoding component of a system, specifically in the vdec module where a use after free condition occurs due to a race condition. This flaw represents a critical security weakness that can be exploited to achieve local privilege escalation, requiring only system execution privileges for successful exploitation. The vulnerability manifests when memory allocated to video decoding processes is freed while still being referenced by other system components, creating a scenario where subsequent memory operations may corrupt or overwrite critical data structures. The race condition aspect indicates that the timing of memory allocation and deallocation operations creates a window where the system state becomes unpredictable and potentially exploitable.
The technical implementation of this vulnerability stems from improper synchronization mechanisms within the vdec module's memory management system. When video decoding processes are initiated and subsequently terminated, the system fails to maintain proper atomicity in memory deallocation operations. This race condition allows malicious code to manipulate the timing of memory operations such that a freed memory block is accessed after it has been reallocated for different purposes. The flaw falls under the CWE-416 category of Use After Free, which is classified as a serious memory safety issue that can result in arbitrary code execution. The vulnerability's classification as a local privilege escalation means that an attacker with basic system execution privileges can leverage this weakness to gain elevated system-level access.
The operational impact of CVE-2023-20685 extends beyond simple memory corruption as it provides a pathway for attackers to elevate their privileges within the system. The lack of user interaction requirement for exploitation makes this vulnerability particularly dangerous as it can be triggered automatically without any direct user involvement. This characteristic aligns with ATT&CK technique T1068 which describes the use of local privilege escalation techniques. The vulnerability affects systems where video decoding is actively used, potentially compromising devices such as smartphones, tablets, or embedded systems that rely on vdec for multimedia processing. Successful exploitation could result in complete system compromise, allowing attackers to execute arbitrary code with elevated privileges, access sensitive data, or establish persistent backdoors.
Mitigation strategies for CVE-2023-20685 should focus on implementing proper memory management synchronization mechanisms within the vdec module. The patch ALPS07608575 addresses this vulnerability by introducing appropriate locking mechanisms and ensuring proper memory lifecycle management during video decoding operations. 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, using address sanitization tools, and conducting regular security audits of multimedia processing components. Organizations should also consider implementing runtime protection mechanisms such as stack canaries, heap metadata protection, and control flow integrity checks to detect and prevent exploitation attempts. The vulnerability highlights the importance of proper race condition handling in kernel-level components and underscores the need for comprehensive memory safety practices in embedded systems and mobile platforms where vdec functionality is prevalent.