CVE-2018-9514 in Android
Summary
by MITRE
In sdcardfs_open of file.c, there is a possible Use After Free due to an unusual root cause. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is not needed for exploitation. Product: Android Versions: Android kernel Android ID: A-111642636 References: N/A
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Analysis
by VulDB Data Team • 03/29/2020
The vulnerability identified as CVE-2018-9514 represents a critical use after free condition within the Android kernel's sdcardfs implementation, specifically in the sdcardfs_open function located in file.c. This flaw exists within the storage subsystem that manages file access between the Android application sandbox and external storage devices, creating a pathway for privilege escalation attacks. The vulnerability's significance lies in its ability to be exploited locally without requiring any additional privileges or user interaction, making it particularly dangerous for mobile device security. The root cause of this issue stems from improper memory management during file descriptor handling within the sdcardfs filesystem driver, which is responsible for bridging the gap between Android's security model and external storage access.
The technical exploitation of this vulnerability occurs when the sdcardfs_open function processes file operations that result in a freed memory pointer being accessed again. This use after free condition typically arises when the kernel's file handling code fails to properly validate or synchronize access to shared memory structures during concurrent file operations. The flaw allows an attacker to potentially manipulate the memory layout and execute arbitrary code with elevated privileges, effectively bypassing the normal Android security boundaries. This type of vulnerability falls under CWE-416, which specifically addresses Use After Free conditions, and represents a classic example of how improper memory management can lead to privilege escalation in kernel space. The attack vector leverages the kernel's handling of file operations through the sdcardfs interface, which is commonly used for accessing external storage devices and shared filesystems within the Android environment.
The operational impact of CVE-2018-9514 extends beyond simple local privilege escalation, as it can potentially enable attackers to gain full system control over affected Android devices. This vulnerability affects the Android kernel directly, meaning that successful exploitation could result in complete compromise of the device's security model and data protection mechanisms. The lack of requirement for user interaction makes this vulnerability particularly concerning for mobile environments where users may not actively monitor for such exploits. The attack could potentially be automated through malicious applications or malware that leverage the kernel vulnerability to elevate their privileges and gain access to sensitive system resources, including user data, device credentials, and other protected information. This flaw also aligns with ATT&CK technique T1068, which covers "Local Privilege Escalation" through kernel exploits, and demonstrates how kernel-level vulnerabilities can be weaponized to bypass multiple layers of Android security controls.
Mitigation strategies for CVE-2018-9514 primarily involve applying the appropriate security patches and updates released by Google and device manufacturers, as this vulnerability was addressed through kernel-level fixes in subsequent Android releases. System administrators and device users should prioritize updating their Android systems to versions that include the patched sdcardfs implementation, particularly focusing on the kernel components that handle file system operations. Additionally, implementing runtime monitoring and anomaly detection for unusual file access patterns or memory allocation behaviors can help identify potential exploitation attempts. The vulnerability highlights the importance of thorough code review and testing for memory management issues in kernel space, particularly within filesystem drivers that handle complex access control scenarios. Organizations should also consider implementing device management policies that enforce automatic security updates and maintain awareness of known vulnerabilities within their mobile device fleets to prevent exploitation of similar kernel-level flaws.