CVE-2016-3850 in Android
Summary
by MITRE
Integer overflow in app/aboot/aboot.c in the Qualcomm bootloader in Android before 2016-08-05 on Nexus 5, 5X, 6P, and 7 (2013) devices allows attackers to gain privileges via a crafted header field in a boot image, aka Android internal bug 27917291 and Qualcomm internal bug CR945164.
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Analysis
by VulDB Data Team • 09/12/2022
The vulnerability described in CVE-2016-3850 represents a critical integer overflow flaw within the Qualcomm bootloader component of Android devices, specifically affecting Nexus 5, 5X, 6P, and 2013 Nexus 7 models. This issue resides in the app/aboot/aboot.c file and was disclosed as part of Android's security updates released in August 2016. The vulnerability stems from improper handling of header fields within boot images, creating a scenario where attackers can manipulate the bootloader's behavior through crafted input data. The integer overflow occurs when the bootloader processes certain header values that exceed the maximum representable value for the integer data type, leading to unexpected program behavior. This particular flaw is categorized under CWE-190 as an integer overflow vulnerability, which is a well-documented weakness in software systems where arithmetic operations produce results that exceed the maximum value that can be stored in the designated data type.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it provides attackers with the capability to bypass critical security mechanisms within the device's boot process. When exploited, the integer overflow allows malicious actors to manipulate the bootloader's execution flow, potentially enabling them to load modified or unauthorized boot images. This creates a persistent threat vector that operates at the lowest level of the device's security architecture, making it particularly dangerous for mobile devices where the bootloader serves as the first line of defense against unauthorized system modifications. The vulnerability's exploitation requires crafting a specific boot image header with manipulated field values, which can then be loaded through various attack vectors such as malicious USB connections, wireless transfers, or compromised update channels. The security implications are further amplified by the fact that this vulnerability affects multiple generations of Nexus devices, creating a widespread attack surface that impacts a significant portion of the Android ecosystem during the affected time period.
The mitigation strategies for CVE-2016-3850 primarily focus on implementing proper input validation and bounds checking within the bootloader code to prevent integer overflow conditions from occurring. Security patches typically involve modifying the aboot.c file to include explicit checks before arithmetic operations that could potentially cause overflow, ensuring that header field values remain within acceptable ranges before processing. Additionally, the vulnerability highlights the importance of secure boot implementation and code signing mechanisms that can detect and prevent unauthorized modifications to the boot process. Organizations should implement comprehensive device management policies that enforce timely security updates and monitor for exploitation attempts through network traffic analysis or endpoint detection systems. The vulnerability also underscores the need for robust firmware validation processes and the importance of maintaining up-to-date security patches, as this issue aligns with ATT&CK technique T1014 for rootkit detection and prevention, where bootloader-level modifications represent a sophisticated attack vector requiring deep system-level security controls. The remediation process involves not only patching the specific integer overflow but also strengthening the overall security posture of the device's boot process through proper code review practices and adherence to secure coding standards that prevent similar vulnerabilities from emerging in future implementations.