CVE-2020-13839 in LG
Summary
by MITRE
An issue was discovered on LG mobile devices with Android OS 7.2, 8.0, 8.1, 9, and 10 (MTK chipsets). Code execution can occur via a custom AT command handler buffer overflow. The LG ID is LVE-SMP-200007 (June 2020).
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Analysis
by VulDB Data Team • 10/22/2020
This vulnerability represents a critical buffer overflow condition within the Android-based mobile operating systems of LG devices that utilize MediaTek chipsets. The flaw exists in the custom AT command handler implementation that processes incoming modem commands through the device's communication interfaces. The vulnerability specifically affects LG mobile devices running Android versions 7.2, 8.0, 8.1, 9, and 10, indicating a widespread impact across multiple generations of Android releases. The AT command handler receives input from the modem subsystem without proper bounds checking, creating an exploitable condition that allows malicious actors to inject arbitrary code into the device's memory space. This type of vulnerability falls under CWE-121, which describes buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations.
The operational impact of this vulnerability extends beyond simple code execution capabilities to encompass potential full device compromise and data exfiltration scenarios. Attackers who can send specially crafted AT commands to the affected devices can leverage this buffer overflow to gain unauthorized code execution privileges within the device's kernel or system-level processes. This presents a significant risk to user privacy and device security, as the attacker could potentially access sensitive information, install malicious applications, or modify system configurations without user consent. The vulnerability's exploitation requires minimal network interaction since AT commands can be sent through various communication channels including SMS, TCP connections, or direct modem interfaces. This aligns with ATT&CK technique T1059.007, which describes the use of command and scripting interpreters for execution, as the overflow allows for arbitrary code execution in the device's operating environment.
The technical nature of this vulnerability stems from improper memory management practices within the custom modem communication handler developed for MediaTek chipsets on LG devices. The buffer overflow occurs when the handler receives AT command payloads that exceed the allocated buffer size, causing memory corruption that can be leveraged to overwrite return addresses, function pointers, or other critical memory structures. This memory corruption allows attackers to redirect execution flow and inject malicious code that executes with the privileges of the modem handler process. The vulnerability's persistence across multiple Android versions suggests that the underlying implementation flaw exists in the chipset-specific firmware rather than being an Android OS-level issue, making remediation more complex and requiring coordinated updates from both LG and MediaTek. The vulnerability's classification as a remote code execution flaw means that attackers could potentially exploit it without physical device access, making it particularly dangerous in mobile environments where devices are constantly connected to cellular networks and other communication services.