CVE-2017-13181 in Android
Summary
by MITRE
In the doGetThumb and getThumbnail functions of MtpServer, there is a possible double free due to not NULLing out a freed pointer. This could lead to an 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: 7.0, 7.1.1, 7.1.2, 8.0, 8.1. Android ID: A-67864232.
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Analysis
by VulDB Data Team • 01/28/2021
The vulnerability described in CVE-2017-13181 represents a critical heap corruption issue within the Media Transfer Protocol (MTP) server implementation of Android operating systems. This flaw exists in the doGetThumb and getThumbnail functions where improper memory management leads to a double free condition that can be exploited to achieve local privilege escalation. The vulnerability affects multiple Android versions including 7.0, 7.1.1, 7.1.2, 8.0, and 8.1, making it a widespread concern across the Android ecosystem. The issue stems from the failure to properly null out a freed pointer, creating a scenario where the same memory location can be freed twice, potentially allowing an attacker to manipulate heap metadata and execute arbitrary code with elevated privileges.
The technical root cause of this vulnerability aligns with CWE-415, which describes improper cleanup of memory resources leading to double-free conditions. When the MtpServer processes thumbnail requests through the affected functions, it fails to maintain proper pointer state management after memory deallocation. This creates a race condition where freed memory can be reallocated and subsequently freed again, corrupting the heap structure. The double free vulnerability occurs because the code does not properly set the freed pointer to NULL, allowing subsequent operations to reference the already deallocated memory location. This type of memory corruption can be leveraged by malicious applications to manipulate the heap layout and potentially control program execution flow through memory corruption attacks.
The operational impact of this vulnerability is severe as it enables local privilege escalation without requiring user interaction or additional execution privileges. An attacker with a sandboxed application running on the device can exploit this flaw to gain elevated privileges and execute code with system-level access. This represents a significant threat to Android device security since the MTP server typically operates with elevated privileges and handles media data transfers from external devices. The vulnerability essentially provides a path for unprivileged code to escalate its privileges to that of the system process, effectively bypassing Android's security model and potentially compromising the entire device. The attack vector is particularly concerning because it does not require user interaction, making it a passive threat that can be exploited during normal device operation when MTP services are active.
The exploitation of this vulnerability can be mapped to several ATT&CK tactics including privilege escalation and code execution. The attack chain typically involves triggering the MTP server functions through malicious media file processing, causing the double free condition, and then leveraging the heap corruption to execute arbitrary code. Mitigation strategies should focus on implementing proper memory management practices including ensuring freed pointers are nullified, adding heap metadata validation, and applying the security patches released by Google. Organizations should prioritize immediate patching of affected Android versions and consider implementing additional runtime protections such as heap randomization and stack canaries to reduce the exploitability of similar memory corruption vulnerabilities. The vulnerability also highlights the importance of proper code review processes and static analysis tools to identify potential memory management issues in system-level components.