CVE-2019-2104 in Android
Summary
by MITRE
In HIDL, safe_union, and other C++ structs/unions being sent to application processes, there are uninitialized fields. This could lead to local information disclosure with no additional execution privileges needed. User interaction is not needed for exploitation. Product: Android. Versions: Android-8.0 Android-8.1 Android-9. Android ID: A-131356202
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Analysis
by VulDB Data Team • 07/02/2020
The vulnerability identified as CVE-2019-2104 resides within the Hardware Interface Definition Language implementation of Android systems, specifically affecting HIDL safe_union and other C++ structs and unions that are transmitted to application processes. This flaw represents a classic case of uninitialized memory access that can potentially expose sensitive data to unauthorized parties. The vulnerability impacts Android versions 8.0, 8.1, and 9, indicating it was present across a significant portion of the Android ecosystem during the time of its discovery. The Android ID A-131356202 further contextualizes this issue within the broader Android security tracking system, highlighting its classification as a medium severity concern that requires attention from device manufacturers and security professionals.
The technical root cause of this vulnerability stems from improper initialization of memory fields within C++ data structures that are designed to be passed between system components and application processes. When these structures are populated with data, certain fields remain uninitialized, creating potential pathways for information leakage. This type of vulnerability aligns with CWE-457, which specifically addresses the use of uninitialized variables in programming contexts. The uninitialized fields essentially contain residual data from previous memory operations, creating a situation where sensitive information from other processes or system components could be inadvertently exposed through these data structures. The flaw manifests when these partially initialized structures are processed by application code, potentially revealing memory contents that should remain confidential.
The operational impact of CVE-2019-2104 is significant despite not requiring user interaction or additional execution privileges for exploitation. Attackers can leverage this vulnerability to perform local information disclosure attacks, potentially accessing sensitive data that was previously stored in memory locations that were not properly cleared or initialized. This type of attack falls under the ATT&CK technique T1005, which involves data from local system storage, and T1059, which encompasses command and scripting interpreter techniques. The vulnerability can be exploited by any application process that receives these malformed data structures, making it particularly dangerous in environments where multiple applications interact with system services through HIDL interfaces. The exposure could potentially include cryptographic keys, personal identification information, or other sensitive data that may have resided in the uninitialized memory regions.
Mitigation strategies for this vulnerability require a multi-layered approach that addresses both the immediate technical flaw and broader security practices. Device manufacturers should implement proper memory initialization routines for all HIDL structures and C++ unions that are designed for inter-process communication, ensuring that all fields are explicitly initialized before data transmission. The Android security team should consider implementing stricter code review processes that specifically check for uninitialized memory access patterns in system-level components. Additionally, developers should adopt defensive programming practices that include explicit initialization of all data structures, particularly those that traverse system boundaries. System administrators should monitor for any unusual data access patterns that might indicate exploitation attempts, while also ensuring that all Android devices receive timely security updates that address this specific vulnerability. The remediation process should also include comprehensive testing of HIDL interfaces to verify that all data structures are properly initialized before being passed between system components and application processes.