CVE-2019-2120 in Android
Summary
by MITRE
In OatFileAssistant::GenerateOatFile of oat_file_assistant.cc, there is a possible file corruption issue due to an insecure default value. 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-7.0 Android-7.1.1 Android-7.1.2 Android-8.0 Android-8.1 Android-9. Android ID: A-130821293.
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Analysis
by VulDB Data Team • 08/01/2020
The vulnerability described in CVE-2019-2120 resides within the Android operating system's oat file assistant component, specifically in the OatFileAssistant::GenerateOatFile function located in oat_file_assistant.cc. This flaw represents a critical security weakness that allows for local privilege escalation without requiring any additional execution privileges or user interaction. The vulnerability stems from an insecure default value that creates a potential file corruption scenario, enabling malicious actors with local access to elevate their privileges to system level. The affected Android versions span across major releases including 7.0, 7.1.1, 7.1.2, 8.0, 8.1, and 9.0, indicating a broad impact across the Android ecosystem. This type of vulnerability falls under CWE-276, which specifically addresses insecure default permissions and inadequate default access controls, making it particularly dangerous as it leverages the system's default behavior to create security breaches.
The technical implementation of this vulnerability involves the generation of oat files, which are Android's optimized application binary format used to improve application performance and execution speed. When the system generates these files, it relies on certain default parameters that are improperly configured, leading to potential corruption of the oat file structure. The insecure default value allows for arbitrary file modification during the generation process, which can be exploited to manipulate system files and gain elevated privileges. This exploitation occurs at the system level where the default file handling behavior is manipulated, bypassing normal security controls that would typically prevent such modifications. The attack vector is particularly concerning because it requires no user interaction, meaning any local process can exploit this weakness, and the privilege escalation happens automatically upon successful exploitation.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it can enable attackers to gain complete control over the Android device. Once escalated to system privileges, malicious actors can modify critical system files, install persistent backdoors, access sensitive user data, and potentially compromise the entire device. The lack of user interaction requirement means this vulnerability can be exploited silently in the background, making detection extremely difficult. The vulnerability's presence across multiple Android versions suggests that it was likely introduced in a common codebase and subsequently affected all versions that inherited the problematic implementation. This makes the exploitation landscape particularly wide-ranging, affecting millions of devices that were not properly patched. The privilege escalation capability aligns with ATT&CK technique T1068, which covers local privilege escalation through insecure file permissions and default configurations.
Mitigation strategies for CVE-2019-2120 should focus on immediate patch deployment through official Android security updates, as the vulnerability was addressed in subsequent security releases. System administrators and device manufacturers must ensure all affected Android versions receive the appropriate patches to correct the insecure default value in the oat file generation process. Additionally, implementing proper file access controls and monitoring for unauthorized modifications to system files can help detect potential exploitation attempts. Organizations should also consider network-level monitoring to identify suspicious activities that may indicate exploitation attempts, particularly around oat file generation and system privilege changes. The vulnerability serves as a reminder of the critical importance of secure default configurations in mobile operating systems, as insecure defaults can provide attackers with automatic escalation paths that bypass traditional security mechanisms. Regular security audits of system components, particularly those handling file generation and system optimization, should be conducted to identify similar insecure default value implementations that could create similar privilege escalation vulnerabilities.