CVE-2019-9253 in Android
Summary
by MITRE
In KeyStore, there is a possible storage of symmetric keys in the TEE instead of the strongbox due to a missing strongbox flag. This could lead to local information disclosure with System execution privileges needed. User interaction is not needed for exploitation. Product: AndroidVersions: Android-10Android ID: A-109769728
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Analysis
by VulDB Data Team • 09/12/2020
The vulnerability identified as CVE-2019-9253 resides within the Android Keystore system, specifically affecting Android 10 and earlier versions. This flaw represents a critical security weakness in how cryptographic keys are stored and managed within the Android security architecture. The vulnerability stems from a missing strongbox flag during the key storage process, which fundamentally alters the security posture of symmetric key management. The Keystore system is designed to provide secure storage for cryptographic keys, with different storage mechanisms available including the TrustZone Execution Environment and the StrongBox secure element. The StrongBox implementation provides enhanced security guarantees through hardware-based isolation and protection mechanisms that are not available in standard TrustZone implementations.
The technical flaw manifests when the system fails to properly specify the strongbox flag during key generation or storage operations. This omission causes the Android Keystore to store symmetric keys in the TrustZone execution environment instead of the more secure StrongBox secure element. The TrustZone environment, while providing basic security isolation, lacks the robust hardware-level protections offered by StrongBox. This misconfiguration creates a scenario where sensitive cryptographic material that should be protected by the enhanced security measures of StrongBox is instead stored in a less secure location. The vulnerability is particularly concerning because it affects the fundamental security model of key storage, potentially exposing symmetric keys to unauthorized access through various attack vectors that might be available in the TrustZone environment.
The operational impact of this vulnerability is significant as it enables local information disclosure when an attacker has system execution privileges. This means that any application or process running with system-level privileges can potentially extract symmetric keys that were intended to be protected by StrongBox security guarantees. The attack does not require user interaction, making it particularly dangerous as it can be exploited automatically without any user awareness or consent. The implications extend beyond simple key exposure, as symmetric keys are often used for encrypting sensitive data, authenticating communications, and providing confidentiality assurances. When these keys are stored in less secure environments, the entire cryptographic infrastructure built upon them becomes compromised. The vulnerability affects the core Android security architecture and represents a failure in the proper enforcement of security policies that should ensure cryptographic keys are stored according to their security requirements.
Mitigation strategies for CVE-2019-9253 focus primarily on ensuring that the proper strongbox flag is set during key generation and storage operations. Android security patches and updates address this by correcting the implementation to properly enforce the StrongBox security requirements for symmetric key storage. Organizations should ensure that all Android devices are updated to versions that contain the appropriate security fixes. System administrators should also implement monitoring to detect any unauthorized key storage operations that might indicate this vulnerability is being exploited. The vulnerability aligns with CWE-310, which addresses cryptographic weaknesses in key management, and maps to ATT&CK technique T1552.004 related to credentials from password storage devices. Additionally, this issue demonstrates the importance of proper security configuration management and the potential consequences of missing security flags in cryptographic implementations. The vulnerability underscores the critical need for robust security controls and proper enforcement of security policies in mobile operating systems, particularly in environments where cryptographic keys are essential for maintaining data confidentiality and system integrity.