CVE-2016-6729 in Android
Summary
by MITRE
An elevation of privilege vulnerability in the Qualcomm bootloader in Android before 2016-11-05 could enable a local malicious application to execute arbitrary code within the context of the kernel. This issue is rated as Critical due to the possibility of a local permanent device compromise, which may require reflashing the operating system to repair the device. Android ID: A-30977990. References: Qualcomm QC-CR#977684.
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Analysis
by VulDB Data Team • 09/30/2022
The vulnerability identified as CVE-2016-6729 represents a critical elevation of privilege flaw within the Qualcomm bootloader component of Android devices, affecting systems prior to the 2016-11-05 security update. This vulnerability resides at the lowest level of the system architecture where the bootloader initializes and loads the operating system, making it a prime target for attackers seeking persistent control over mobile devices. The issue stems from improper validation mechanisms within the bootloader's boot process that fails to adequately verify the integrity and authenticity of components being loaded into memory. This fundamental flaw allows a malicious application with local access to exploit the bootloader's trust model and gain unauthorized kernel-level execution privileges.
The technical implementation of this vulnerability involves a failure in the bootloader's verification procedures that typically occur during the device's boot sequence. When a device boots up, the Qualcomm bootloader is responsible for validating the authenticity of the operating system components before they are loaded into memory and executed. The flaw occurs when the bootloader accepts potentially malicious code without proper cryptographic verification or integrity checks, allowing an attacker to inject code that executes with kernel-level privileges. This represents a classic example of a bootkit attack vector where the compromise occurs at the very foundation of the device's security architecture, making it extremely difficult to detect or remediate through standard software patches. The vulnerability maps directly to CWE-284, which addresses improper access control in bootloaders and firmware components, and aligns with ATT&CK technique T1068, which covers local privilege escalation through kernel exploits.
The operational impact of this vulnerability extends far beyond typical application-level security breaches, as it enables complete device compromise with persistent access that can survive reboots and standard security measures. A malicious application that successfully exploits this vulnerability can execute arbitrary code within the kernel context, effectively bypassing all traditional Android security boundaries and access controls. This level of privilege allows the attacker to modify system files, install persistent backdoors, access all device data, and potentially disable security features entirely. The severity classification as Critical reflects the permanence of this compromise, as the vulnerability can be exploited repeatedly without requiring additional user interaction after the initial compromise. Recovery from such an attack typically requires complete device re-flashing, which not only results in data loss but also represents a significant inconvenience for end users and a substantial burden for device manufacturers who must manage large-scale recall and repair operations.
Mitigation strategies for CVE-2016-6729 focus primarily on applying the relevant Android security patches released by Google and Qualcomm, which include updated bootloader firmware and enhanced verification mechanisms. Device manufacturers must ensure timely deployment of these patches through their regular update cycles, as the vulnerability remains exploitable until the security fixes are properly installed. Additionally, users should maintain awareness of their device's security status and promptly install available updates, particularly those addressing bootloader vulnerabilities. The recommended approach includes implementing proper firmware update mechanisms that prevent downgrade attacks and ensure only verified, signed components are loaded during the boot process. Organizations should also consider implementing device management policies that enforce security patch compliance and monitor for signs of exploitation attempts. From a defense perspective, this vulnerability highlights the importance of supply chain security and the need for robust verification processes at every level of the device architecture, as the bootloader represents the first line of defense against sophisticated attacks that target the most fundamental system components.