CVE-2018-9523 in Android
Summary
by MITRE
In Parcel.writeMapInternal of Parcel.java, there is a possible parcel serialization/deserialization mismatch due to improper input validation. 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-112859604
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Analysis
by VulDB Data Team • 04/13/2020
The vulnerability identified as CVE-2018-9523 resides within the Android operating system's parcel serialization mechanism, specifically in the Parcel.writeMapInternal method implementation. This flaw represents a critical security issue that allows for local privilege escalation without requiring any additional execution privileges or user interaction for exploitation. The vulnerability manifests as a serialization/deserialization mismatch that occurs when Android applications attempt to marshal and unmarshal map data structures through the Binder IPC mechanism. The issue stems from insufficient input validation during the parcel writing process, creating a potential attack vector where malicious code can manipulate the serialized data structure to gain elevated privileges on the device. This 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 platform ecosystem. The flaw operates at the system level within the Android framework, making it particularly dangerous as it can be exploited by any application with the appropriate permissions to interact with the Binder interface.
The technical root cause of this vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow conditions. The improper input validation in the Parcel.writeMapInternal method creates a scenario where the system fails to properly validate the size and structure of map data during serialization. When an application writes a map structure to a parcel, the system does not adequately verify that the data conforms to expected boundaries or structures, allowing for potential manipulation of the serialized data. The attack vector leverages the Android Binder IPC system, which is fundamental to inter-process communication within the Android operating system. This system allows applications to communicate with each other and with system services using a mechanism that relies heavily on proper parcel serialization. The vulnerability's exploitation requires no user interaction because it operates entirely within the system's internal communication mechanisms, making it particularly insidious as it can be triggered automatically when applications attempt to perform normal communication operations.
The operational impact of CVE-2018-9523 is severe and far-reaching, as it enables local privilege escalation that can allow malicious applications to gain system-level privileges without requiring additional attack vectors or user interaction. Once exploited, an attacker can potentially gain full control over the device, access all user data, install malicious applications, and modify system configurations. The vulnerability's presence across multiple Android versions means that a significant portion of Android devices remain susceptible to this attack, particularly affecting users of Android 7.0 through 9.0 versions. The exploitation process involves crafting malicious map data structures that, when serialized and subsequently deserialized, cause the system to behave unexpectedly, potentially leading to privilege elevation. This type of vulnerability is classified under the ATT&CK technique T1068, which describes 'Exploitation for Privilege Escalation', making it a particularly concerning threat in the context of mobile device security. The vulnerability essentially allows for a form of code injection or memory corruption that bypasses normal Android security boundaries, enabling applications to perform actions that should be restricted to system-level processes.
Mitigation strategies for CVE-2018-9523 primarily involve applying the official Android security patches released by Google, which address the underlying serialization validation issues in the Parcel.java implementation. System administrators and device manufacturers should prioritize immediate deployment of these patches across affected Android versions, particularly focusing on devices running Android 7.0 through 9.0. Organizations should implement robust application sandboxing policies to limit the potential impact of compromised applications, while also monitoring for any suspicious behavior that might indicate exploitation attempts. The vulnerability's nature suggests that additional input validation should be implemented at multiple levels within the Android framework, including both serialization and deserialization phases of the parcel mechanism. Security teams should also consider implementing runtime monitoring for abnormal parcel operations and establish incident response procedures specifically designed to address privilege escalation vulnerabilities. Device users should be advised to keep their Android systems updated with the latest security patches and avoid installing untrusted applications that might exploit this vulnerability. The fix typically involves strengthening the validation logic in the writeMapInternal method to ensure proper bounds checking and structure validation during the serialization process, preventing malformed data from causing unexpected behavior during deserialization.