CVE-2019-2136 in Android
Summary
by MITRE
In Status::readFromParcel of Status.cpp, there is a possible out of bounds read due to improper input validation. This could lead to local information disclosure 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-132650049.
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Analysis
by VulDB Data Team • 08/01/2020
The vulnerability identified as CVE-2019-2136 resides within the Android system's Status::readFromParcel method implementation in the Status.cpp file. This represents a critical security flaw that manifests as an out-of-bounds read condition, where the application fails to properly validate input data before processing. The issue stems from insufficient boundary checking during the deserialization of parcelable objects, specifically when handling status information within the Android framework. The vulnerability affects multiple Android versions including 7.0, 7.1.1, 7.1.2, 8.0, 8.1, and 9.0, indicating a widespread impact across the Android ecosystem. The flaw is classified under CWE-129 as an Improper Validation of Array Index, which directly relates to the lack of proper input validation mechanisms that should prevent access to memory locations beyond the allocated buffer boundaries. From an operational perspective, this vulnerability enables local information disclosure attacks where malicious applications or processes can read memory contents that they should not have access to, potentially exposing sensitive data such as system credentials, user information, or other confidential parameters stored in memory. The attack vector requires no user interaction and can be exploited with no additional execution privileges, making it particularly dangerous as it can be triggered automatically by the system itself. This vulnerability aligns with ATT&CK technique T1059.001 for Command and Scripting Interpreter and T1068 for Exploitation for Privilege Escalation, as it provides a pathway for unauthorized data access and information gathering. The security implications extend beyond simple data exposure, as the leaked information could potentially be used to facilitate further attacks or compromise the integrity of the Android system. The root cause lies in the improper handling of serialized data structures within the Android framework's parcelable system, where the readFromParcel method does not adequately validate the size or structure of incoming data before attempting to access array elements. This type of vulnerability is particularly concerning in mobile environments where system resources are limited and memory management is critical for overall system stability and security.
The exploitation of CVE-2019-2136 demonstrates how seemingly minor input validation flaws can lead to significant security consequences within complex systems. The vulnerability specifically targets the Android framework's inter-process communication mechanisms, where Status objects are serialized and transmitted between different components or applications. When a malicious actor can manipulate the input data to the readFromParcel method, they can cause the system to read beyond the intended memory boundaries, potentially accessing sensitive information from adjacent memory locations. The lack of proper bounds checking in the array access operations creates a predictable pattern that attackers can exploit to extract useful information from the system's memory space. This vulnerability represents a classic example of how insufficient validation of untrusted input data can lead to information disclosure attacks, which are among the most common types of security flaws in mobile operating systems. The impact is particularly severe because it affects the core Android framework components, meaning that any application or system service that relies on proper status handling could be vulnerable to this attack. The vulnerability's classification as local information disclosure means that it primarily affects the device's own security posture rather than creating network-based attack vectors, but it still represents a significant threat to user privacy and system integrity. Security researchers have noted that such flaws often remain undetected for extended periods due to the complexity of Android's framework and the numerous code paths that can lead to similar vulnerabilities.
Mitigation strategies for CVE-2019-2136 should focus on implementing robust input validation mechanisms within the Android framework's parcelable handling code. The most effective approach involves adding comprehensive bounds checking before any array access operations, ensuring that all input data is properly validated against expected size constraints. Android developers and system maintainers should implement defensive programming practices that include explicit range validation for all array indexing operations, particularly in methods that process serialized data. The fix should involve modifying the Status::readFromParcel method to verify that array indices do not exceed the allocated buffer boundaries before attempting to read data. This type of mitigation aligns with security best practices outlined in the OWASP Mobile Top 10 and follows the principle of least privilege by ensuring that applications can only access memory locations they are explicitly authorized to reach. Organizations should also implement regular security audits of their Android applications to identify similar vulnerabilities in custom code that may be susceptible to the same type of out-of-bounds read conditions. Additionally, system updates and patches should be applied immediately upon availability, as Google has addressed this vulnerability in subsequent Android releases through improved input validation mechanisms. The vulnerability serves as a reminder of the importance of comprehensive testing procedures, particularly for security-sensitive code paths that handle untrusted data from external sources. Regular code reviews focusing on memory management and input validation practices can help prevent similar issues from emerging in future Android versions or third-party applications that rely on the same framework components.