CVE-2020-0403 in Android
Summary
by MITRE
In the FPC TrustZone fingerprint App, there is a possible invalid command handler due to an exposed test feature. This could lead to local escalation of privilege in the TEE, with System execution privileges required. User interaction is not needed for exploitation.Product: AndroidVersions: Android kernelAndroid ID: A-131252923
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Analysis
by VulDB Data Team • 09/18/2020
The vulnerability identified as CVE-2020-0403 resides within the FPC TrustZone fingerprint application, a critical component of Android's security architecture that operates within the Trusted Execution Environment. This flaw represents a significant security weakness in the implementation of the fingerprint authentication system, where an exposed test feature creates an invalid command handler that can be exploited by malicious actors. The vulnerability specifically affects Android kernel versions and is catalogued under Android ID A-131252923, indicating its integration with Google's internal vulnerability tracking system. The presence of this test feature in production code demonstrates a critical oversight in the security review process, as such debugging mechanisms should never be accessible in deployed environments.
The technical implementation flaw stems from improper handling of command processing within the TrustZone environment, where the exposed test feature allows unauthorized command execution that bypasses normal security controls. This invalid command handler creates a path for privilege escalation from a regular user context to system execution privileges, fundamentally undermining the security isolation that the Trusted Execution Environment is designed to maintain. The vulnerability's classification as a local privilege escalation means that an attacker must already have some level of access to the device, but once exploited, can gain the elevated privileges necessary to compromise the entire system. The attack vector leverages the fact that test commands intended for development and debugging purposes remain enabled in the production fingerprint application, creating an unintended attack surface.
The operational impact of CVE-2020-0403 extends beyond simple privilege escalation, as it represents a complete breakdown in the security boundaries of the Trusted Execution Environment. When an attacker successfully exploits this vulnerability, they gain access to the TEE's secure processing capabilities, potentially allowing them to extract sensitive biometric data, modify secure storage, or even bypass other security mechanisms within the device. This type of vulnerability aligns with CWE-254, which addresses security weaknesses in the implementation of security features, and specifically relates to CWE-787, which covers out-of-bounds writes and reads in security contexts. The exploitation of this vulnerability could enable attackers to perform operations that are typically restricted to system-level processes, effectively neutralizing the security benefits that the TrustZone architecture provides.
Mitigation strategies for this vulnerability require immediate attention from device manufacturers and system administrators, as the flaw exists in the core security infrastructure of affected Android devices. The primary remediation involves disabling or removing the exposed test feature from the fingerprint application, ensuring that no debugging mechanisms remain accessible in production environments. Additionally, comprehensive security audits should be conducted to identify other potential test features or debugging capabilities that may have been inadvertently left enabled. From an ATT&CK framework perspective, this vulnerability maps to T1068, which covers local privilege escalation, and T1548, which addresses abuse of system permissions. Device vendors should implement proper code review processes that specifically validate the removal of development and debugging features before production deployment, ensuring that all security-relevant components operate within their intended security boundaries. The vulnerability also highlights the importance of following secure development lifecycle practices and conducting thorough penetration testing of security-sensitive components within the TEE environment.