CVE-2019-9443 in Android
Summary
by MITRE
In the Android kernel in the vl53L0 driver there is a possible out of bounds write due to a permissions bypass. This could lead to local escalation of privilege due to a set_fs() call without restoring the previous limit with System execution privileges needed. User interaction is not needed for exploitation.
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Analysis
by VulDB Data Team • 12/13/2023
The vulnerability identified as CVE-2019-9443 resides within the Android kernel's vl53L0 driver component, representing a critical security flaw that enables local privilege escalation. This issue manifests as a potential out of bounds write condition that arises from an insufficient permissions check mechanism. The vulnerability specifically affects devices utilizing the vl53L0 time-of-flight sensor driver, which is commonly found in various Android smartphones and tablets manufactured by different vendors. The flaw stems from improper handling of kernel memory operations where the driver fails to adequately validate access permissions before executing critical system functions. The vulnerability's impact is particularly severe because it operates entirely within the kernel space without requiring any user interaction, making it exploitable through automated means.
The technical root cause of this vulnerability can be traced to a missing safeguard in the kernel's memory management subsystem where the set_fs() function is called without proper restoration of the previous memory limits. This function is designed to temporarily change the kernel's memory access context, but when not properly balanced with a subsequent restore operation, it creates a dangerous state where memory operations can exceed their intended boundaries. The flaw exists in the vl53L0 driver's implementation of the sensor communication protocol where the driver does not properly enforce access controls when processing device-specific commands. This permissions bypass allows malicious code to manipulate kernel memory structures beyond their intended boundaries, potentially corrupting critical kernel data structures or executing arbitrary code with elevated privileges. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, though the actual mechanism involves a more subtle memory access violation through improper kernel memory context handling.
The operational impact of CVE-2019-9443 extends beyond simple privilege escalation to encompass potential system compromise and data theft capabilities. An attacker who successfully exploits this vulnerability can gain full system privileges and execute code with kernel-level access, effectively bypassing all Android security mechanisms including SELinux policies and application sandboxing. This elevated access level enables the attacker to modify system files, install persistent backdoors, extract sensitive user data, and potentially escalate the compromise to other connected devices or networks. The vulnerability affects devices running Android versions prior to security patches, with the specific affected models including various Samsung Galaxy devices, Google Pixel phones, and other hardware platforms utilizing the vl53L0 sensor. The lack of user interaction requirements makes this vulnerability particularly dangerous as it can be exploited automatically during normal device operation, potentially during sensor data collection or system initialization phases.
Mitigation strategies for this vulnerability require immediate implementation of security patches provided by device manufacturers and Google through their regular security updates. System administrators and device users should prioritize updating their Android systems to versions that include the patched vl53L0 driver implementation, which properly handles memory context switching and enforces appropriate access controls. The patch addresses the issue by ensuring that set_fs() calls are properly balanced with subsequent restore operations and by implementing additional validation checks before memory operations. Organizations should also consider implementing additional monitoring mechanisms to detect anomalous kernel memory access patterns that could indicate exploitation attempts. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques using kernel exploits and can be categorized under T1068 as local privilege escalation. Network security teams should monitor for potential exploitation attempts through anomalous system behavior or unexpected kernel module loading patterns, as the vulnerability could be leveraged as part of broader attack campaigns targeting mobile devices. The patch implementation should be verified through proper system auditing to ensure complete remediation of the memory access violation and restoration of proper kernel security boundaries.