CVE-2017-13217 in Android
Summary
by MITRE
In DisplayFtmItem in the bootloader, there is an out-of-bounds write due to reading a string without verifying that it's null-terminated. This could lead to a secure boot bypass and a local elevation of privilege enabling code execution as a privileged process with no additional execution privileges needed. User interaction is not needed for exploitation. Product: Android. Versions: Android kernel. Android ID: A-68269077.
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Analysis
by VulDB Data Team • 01/29/2021
The vulnerability identified as CVE-2017-13217 resides within the bootloader component of Android devices, specifically in the DisplayFtmItem function where improper string handling leads to a critical out-of-bounds write condition. This flaw exists in the Android kernel and represents a fundamental security weakness that can be exploited without any user interaction, making it particularly dangerous as it can be triggered automatically during device boot processes. The vulnerability stems from inadequate input validation where the system reads a string without first verifying that it is properly null-terminated, creating a scenario where memory boundaries are exceeded during string processing operations. This type of flaw falls under CWE-121 which categorizes buffer overflow conditions, specifically manifesting as heap-based buffer overflows that can be leveraged for privilege escalation. The security implications are severe as this vulnerability can bypass secure boot mechanisms that are designed to ensure only authenticated and trusted code executes during the boot process, effectively undermining the core security architecture of Android devices.
The technical exploitation of this vulnerability enables an attacker to achieve local elevation of privilege by executing code with elevated permissions, essentially allowing malicious code to run with the same privileges as system-level processes. The out-of-bounds write condition creates opportunities for memory corruption that can be manipulated to overwrite critical system structures or function pointers, potentially redirecting execution flow to malicious code. This type of attack vector aligns with ATT&CK technique T1068 which covers "Local Privilege Escalation" and specifically targets the kernel level where the vulnerability exists. The absence of user interaction requirements means that exploitation can occur silently during device boot, making it particularly stealthy and difficult to detect. The vulnerability affects the bootloader phase where the system initializes hardware and loads the operating system, making it one of the earliest and most critical points where an attacker can gain control over the device's execution environment.
The operational impact of CVE-2017-13217 extends beyond simple privilege escalation as it fundamentally compromises the integrity of the device's boot process and secure execution environment. When exploited, this vulnerability can enable attackers to bypass security measures that are supposed to prevent unauthorized code execution, potentially allowing for full device compromise including data theft, persistent backdoor installation, and complete control over the device's functionality. The vulnerability affects Android devices running kernel versions that include the vulnerable DisplayFtmItem function, making it a widespread concern across multiple device models and manufacturers. The exploitation of this vulnerability can result in permanent device compromise, as the attacker gains access to system-level resources and can modify critical system files or install persistent malware that survives device reboots. This represents a significant risk to enterprise security and user privacy, particularly in environments where mobile devices are used to access sensitive corporate data or handle confidential information.
Mitigation strategies for CVE-2017-13217 require immediate firmware updates from device manufacturers and system administrators to patch the vulnerable bootloader components. The most effective approach involves applying security patches that properly validate string termination before processing, thereby preventing the out-of-bounds write condition from occurring. Organizations should implement comprehensive device management policies that ensure timely deployment of security updates across all Android devices in their inventory, particularly focusing on the bootloader and kernel components. Additionally, monitoring for suspicious boot behavior or unauthorized code execution can help detect potential exploitation attempts, although the silent nature of this vulnerability makes detection particularly challenging. Device manufacturers should also consider implementing additional runtime protections such as stack canaries or memory protection mechanisms that can help detect or prevent exploitation attempts. The vulnerability demonstrates the critical importance of secure coding practices in low-level system components where memory corruption can lead to complete system compromise, reinforcing the need for rigorous input validation and boundary checking in all system-level code.