CVE-2019-9403 in Android
Summary
by MITRE
In cn-cbor, there is a possible out of bounds read due to improper casting. This could lead to remote information disclosure with no additional execution privileges needed. User interaction is needed for exploitation. Product: AndroidVersions: Android-10Android ID: A-113512324
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Analysis
by VulDB Data Team • 09/13/2020
The vulnerability identified as CVE-2019-9403 resides within the cn-cbor library, a lightweight C implementation for parsing and generating cbor data format. This library serves as a critical component in various Android system services and applications that handle structured data encoding. The flaw manifests as an out-of-bounds read condition that occurs during the parsing of malformed cbor payloads, specifically when the library performs improper casting operations on data structures. This vulnerability affects Android 10 systems and is tracked under Android ID A-113512324, indicating its significance within the Android security ecosystem.
The technical root cause of this vulnerability stems from insufficient validation during the cbor parsing process where the cn-cbor library fails to properly validate array bounds before accessing memory locations. When processing crafted cbor data containing malformed array structures, the library performs casting operations that do not adequately check for valid memory boundaries, leading to memory access violations. This improper casting behavior creates a scenario where the application reads data from memory locations beyond the intended array boundaries, potentially exposing sensitive information stored in adjacent memory regions. The vulnerability is classified as CWE-129, representing an insufficient validation of array indices, and aligns with ATT&CK technique T1059.001 for command and scripting interpreter usage in exploitation contexts.
The operational impact of CVE-2019-9403 presents a significant risk for remote information disclosure attacks. An attacker can craft malicious cbor payloads that, when processed by vulnerable applications, trigger the out-of-bounds read condition. This allows for the extraction of sensitive data from memory locations adjacent to the corrupted array, potentially including cryptographic keys, user credentials, or other confidential information. The vulnerability requires user interaction for exploitation, meaning that a malicious payload must be delivered through a legitimate user action such as opening a malicious file or visiting a compromised website. However, the lack of additional execution privileges required makes this attack vector particularly concerning as it can be executed without elevated permissions. The exploitation process typically involves sending crafted cbor data to applications that utilize the cn-cbor library, with the attack succeeding when the library attempts to parse the malformed input and triggers the memory access violation.
Mitigation strategies for CVE-2019-9403 should prioritize immediate patching of affected Android system components and applications that rely on the cn-cbor library. Android security updates released in Q2 2019 addressed this vulnerability through library updates that implement proper bounds checking and casting validation. Organizations should also implement network-level controls to monitor and filter potentially malicious cbor data traffic, particularly in environments where such data flows through networked applications. Additional defensive measures include input validation at application layers, implementing proper error handling for parsing operations, and conducting regular security assessments of cbor processing components. The vulnerability demonstrates the importance of robust memory management practices in C-based libraries and highlights the necessity of thorough testing with malformed inputs to prevent similar issues in other components that handle structured data parsing.