CVE-2018-21051 in Samsung
Summary
by MITRE
An issue was discovered on Samsung mobile devices with N(7.x) and O(8.x) (Exynos chipsets) software. There is an invalid free in the fingerprint Trustlet, leading to arbitrary code execution. The Samsung ID is SVE-2018-12853 (October 2018).
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Analysis
by VulDB Data Team • 10/07/2020
This vulnerability exists within Samsung mobile devices running Android Nougat 7.x and Oreo 8.x operating systems that utilize Exynos chipsets. The flaw resides in the fingerprint Trustlet component which represents a security-critical subsystem responsible for handling biometric authentication data. The Trustlet operates in a trusted execution environment separate from the main operating system, making it a prime target for attackers seeking to escalate privileges and gain unauthorized access to sensitive biometric information.
The technical implementation flaw manifests as an invalid free operation within the fingerprint Trustlet code structure. This memory management error occurs when the Trustlet attempts to release memory that was either not properly allocated or has already been freed, creating a memory corruption vulnerability. Such invalid free operations typically result from improper pointer management or lack of proper bounds checking in the Trustlet's memory handling routines. The vulnerability stems from insufficient input validation and memory safety checks within the fingerprint authentication subsystem, allowing attackers to manipulate memory states through crafted inputs.
The operational impact of this vulnerability is severe as it enables arbitrary code execution within the Trustlet environment, which operates with elevated privileges and direct access to sensitive biometric data. Attackers can exploit this weakness to bypass the fingerprint authentication mechanism entirely, potentially gaining root access to the device or extracting stored fingerprint templates and other biometric information. This represents a critical escalation from a simple authentication bypass to a full system compromise, as the Trustlet environment typically has access to cryptographic keys and sensitive user data that should remain protected from unauthorized access. The vulnerability affects devices where the Trustlet component handles fingerprint data processing, making it particularly concerning for mobile devices that rely heavily on biometric authentication for security.
Mitigation strategies should focus on both immediate patching and architectural improvements to prevent similar vulnerabilities in the future. Samsung released security updates addressing this specific issue, which should be applied immediately to all affected devices. Organizations should implement device management policies to ensure timely patch deployment and monitor for similar memory corruption vulnerabilities in other trusted execution environments. The vulnerability aligns with CWE-415 which describes double free errors, and represents a classic example of how memory safety issues in trusted environments can lead to complete system compromise. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques and credential access, potentially enabling adversaries to establish persistent access to mobile devices and extract sensitive biometric information that could be used for identity theft or unauthorized access to other systems.