CVE-2018-9515 in Android
Summary
by MITRE
In sdcardfs_create and sdcardfs_mkdir of inode.c, there is a possible memory corruption due to improper locking. 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-111641492 References: N/A
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 06/06/2024
The vulnerability identified as CVE-2018-9515 resides within the Android kernel's sdcardfs implementation, specifically affecting the sdcardfs_create and sdcardfs_mkdir functions in the inode.c file. This memory corruption flaw stems from improper locking mechanisms that fail to adequately protect shared resources during concurrent access scenarios. The vulnerability represents a critical security weakness that allows local attackers to escalate their privileges without requiring additional execution privileges or user interaction, making it particularly dangerous in mobile environments where users may not be aware of the underlying system compromise.
The technical flaw manifests through inadequate synchronization primitives within the sdcardfs filesystem implementation, which is designed to provide a compatibility layer between the legacy sdcard filesystem and the newer ext4 filesystem. When multiple processes attempt to create files or directories simultaneously through the sdcardfs interface, the missing or insufficient locking mechanisms can lead to race conditions that corrupt kernel memory structures. This memory corruption can be exploited to manipulate kernel data structures and ultimately gain elevated privileges, as the attacker can leverage the corrupted memory to execute arbitrary code with kernel-level permissions. The vulnerability directly maps to CWE-362, which describes a race condition in the context of improper locking, and aligns with ATT&CK technique T1068 which covers the exploitation of local privilege escalation vulnerabilities.
The operational impact of CVE-2018-9515 extends beyond simple privilege escalation, as it fundamentally undermines the security model of Android devices by allowing unauthorized access to kernel-level resources. Attackers can leverage this vulnerability to bypass security boundaries that normally prevent user-space applications from accessing sensitive system resources or executing privileged operations. The lack of user interaction requirement makes this vulnerability particularly concerning for mobile devices where users may be unaware of ongoing exploitation attempts. Once successfully exploited, the attacker can access the device's full functionality including the ability to read all user data, modify system files, install malicious applications, and potentially establish persistent backdoors. The vulnerability affects all Android versions that incorporate the affected kernel code, making it a widespread concern across the mobile platform ecosystem.
Mitigation strategies for CVE-2018-9515 require immediate patching of affected Android kernel versions through official security updates from device manufacturers and carriers. Organizations should implement proactive monitoring for exploitation attempts and ensure that all Android devices receive timely security updates to address the underlying kernel vulnerability. System administrators should also consider implementing additional security controls such as kernel module integrity checking and monitoring for suspicious privilege escalation attempts. The vulnerability highlights the importance of proper locking mechanisms in kernel code and serves as a reminder of the critical need for thorough security testing of filesystem implementations that handle concurrent access scenarios. Device manufacturers should also consider implementing additional runtime protections and exploit prevention mechanisms to mitigate the risk of exploitation even if patches are not immediately available.