CVE-2018-9559 in Android
Summary
by MITRE
In persist_set_key and other functions of cryptfs.cpp, there is a possible out-of-bounds write due to an uncaught error. 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-112731440.
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Analysis
by VulDB Data Team • 04/18/2020
The vulnerability identified as CVE-2018-9559 represents a critical out-of-bounds write flaw within the Android cryptfs implementation that affects multiple versions of the Android operating system. This issue resides in the persist_set_key function and related cryptographic functions within the cryptfs.cpp file, which serves as the core component responsible for managing full-disk encryption operations on Android devices. The vulnerability stems from an unhandled error condition that occurs during key persistence operations, creating a scenario where memory corruption can occur when the system attempts to write data beyond allocated buffer boundaries.
The technical nature of this flaw places it squarely within CWE-121, which categorizes buffer overflow conditions, and more specifically aligns with CWE-787, representing out-of-bounds write vulnerabilities. The vulnerability manifests when the cryptfs subsystem fails to properly validate input parameters or handle error states during key management operations, leading to a situation where malicious code or an attacker with local access could exploit this condition to write data beyond intended memory boundaries. This type of vulnerability is particularly dangerous because it operates at the system level where encryption keys are managed, potentially allowing an attacker to manipulate the encryption state or gain unauthorized access to encrypted data.
The operational impact of CVE-2018-9559 is severe and directly enables local privilege escalation without requiring any additional execution privileges or user interaction. This means that any application running with standard user privileges could potentially exploit this vulnerability to elevate its privileges to system level, effectively compromising the entire device. The attack vector is particularly concerning because it does not require user interaction, making it a silent threat that can be exploited automatically upon device boot or during normal operation. The vulnerability affects all listed Android versions including 7.0, 7.1.1, 7.1.2, 8.0, 8.1, and 9.0, indicating this flaw has persisted across multiple major releases, suggesting a fundamental issue in the encryption subsystem design that was not properly addressed in security patches.
From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques under tactic T1068, where an attacker leverages local system flaws to gain elevated privileges. The exploitation process would likely involve crafting specific inputs that trigger the error condition in cryptfs.cpp, allowing for memory corruption that can be manipulated to execute arbitrary code with system-level privileges. The vulnerability's classification as a local privilege escalation means that it falls under the category of techniques that do not require network connectivity or external attack vectors, making it particularly dangerous in environments where devices are not regularly updated or patched.
Mitigation strategies for CVE-2018-9559 should prioritize immediate patching of affected Android versions, as Google released security updates addressing this specific vulnerability through the Android Security Bulletins. Organizations should implement comprehensive device management policies to ensure all Android devices receive security updates promptly, particularly focusing on the encryption subsystem components. Additionally, system administrators should monitor for any signs of unauthorized privilege escalation attempts and consider implementing additional security controls such as mandatory access controls or application sandboxing to limit the potential impact of exploitation. The vulnerability highlights the critical importance of proper error handling in system-level cryptographic operations and underscores the need for robust input validation and boundary checking in security-critical code components.