CVE-2016-3939 in Android
Summary
by MITRE
drivers/video/msm/mdss/mdss_debug.c in the Qualcomm video driver in Android before 2016-10-05 on Nexus 5X, Nexus 6, Nexus 6P, and Android One devices allows attackers to gain privileges via a crafted application, aka Android internal bug 30874196 and Qualcomm internal bug CR 1001224.
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Analysis
by VulDB Data Team • 09/22/2022
The vulnerability described in CVE-2016-3939 represents a critical privilege escalation flaw within the Qualcomm MSM (Mobile Services Module) video driver component of Android operating systems. This issue affects specific Google Nexus devices including the Nexus 5X, Nexus 6, Nexus 6P, and Android One models, with the vulnerability being present in Android versions prior to the 2016-10-05 security patch. The flaw exists in the mdss_debug.c file which is part of the Qualcomm driver implementation responsible for managing display subsystem debugging features.
The technical nature of this vulnerability stems from improper input validation and privilege handling within the video driver's debugging interface. Attackers can exploit this weakness by crafting a malicious application that leverages the vulnerable debug functionality to escalate privileges from a regular application context to system-level privileges. This occurs because the driver fails to properly verify the authenticity and authorization of requests made to its debugging interfaces, allowing unprivileged code to execute privileged operations. The vulnerability specifically relates to how the system handles debug commands that should only be accessible to kernel-level components or authorized system services.
From an operational impact perspective, this vulnerability creates a severe security risk as it enables attackers to gain full system control without requiring physical access or additional exploitation vectors. Once successfully exploited, the malicious application could access all system resources, modify critical system files, install persistent backdoors, and potentially compromise user data confidentiality and integrity. The attack surface is particularly concerning given that these devices were widely deployed and the vulnerability affected multiple high-profile Android models. This flaw directly violates the principle of least privilege and undermines the fundamental security model of the Android operating system.
The vulnerability aligns with CWE-269: "Improper Privilege Management" and represents a classic case of insufficient access control mechanisms in kernel drivers. From an adversary perspective, this vulnerability maps to ATT&CK technique T1068: "Exploitation for Privilege Escalation" and T1059: "Command and Scripting Interpreter" as attackers can leverage the debug interface to execute arbitrary commands with elevated privileges. Organizations and users should prioritize immediate patching of affected devices to remediate this vulnerability, as the exploitation requires no special hardware or complex attack chains beyond crafting a malicious application. The fix implemented by Qualcomm and Google involved strengthening input validation in the debug interface and ensuring proper privilege checks before executing sensitive operations within the MSM video driver subsystem.
This vulnerability demonstrates the critical importance of secure driver development practices and proper privilege separation in mobile operating systems. The flaw highlights how seemingly benign debugging features can become attack vectors when not properly secured, emphasizing the need for comprehensive security reviews of kernel-level components. The exploitation capability of this vulnerability makes it particularly dangerous in environments where mobile devices may be compromised through various attack vectors, as the privilege escalation could provide attackers with persistent access to sensitive device functions and data.