CVE-2020-0469 in Android
Summary
by MITRE • 12/15/2020
In addEscrowToken of LockSettingsService.java, there is a possible loss of the synthetic password due to logic error. This could lead to local denial of service with no additional execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android-11Android ID: A-168692734
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Analysis
by VulDB Data Team • 12/17/2020
The vulnerability identified as CVE-2020-0469 resides within the Android operating system's lock settings service implementation, specifically in the addEscrowToken method of LockSettingsService.java. This flaw represents a logic error that can result in the permanent loss of synthetic passwords, which are critical components of Android's device security infrastructure. The synthetic password mechanism serves as a backup authentication method that allows users to regain access to their devices when they forget their primary lock screen credentials. When this logic error occurs, the system fails to properly maintain or store these synthetic passwords, creating a scenario where users may permanently lose access to their devices.
The technical nature of this vulnerability stems from a flawed implementation within the LockSettingsService component that manages device locking mechanisms and credential storage. The addEscrowToken method, which is responsible for adding and managing escrow tokens used for synthetic password generation, contains a logic error that prevents proper token handling and storage. This error manifests as a failure to correctly persist synthetic password information within the system's credential management framework. The vulnerability operates at the system level within Android's security architecture, specifically affecting the lock settings service that governs device authentication and access control mechanisms.
The operational impact of CVE-2020-0469 is significant as it can lead to local denial of service conditions where users become permanently locked out of their devices. This represents a critical security flaw because it directly affects device usability and user access to their personal data. The vulnerability does not require any additional execution privileges for exploitation, meaning that any local user with access to the device can potentially trigger this condition. Furthermore, no user interaction is necessary for exploitation, making this vulnerability particularly concerning as it can be triggered automatically without user awareness or consent. The attack surface is limited to local device access, but the consequences are severe as they result in complete device inaccessibility.
From a cybersecurity perspective, this vulnerability aligns with CWE-284 (Improper Access Control) and CWE-707 (Improper Neutralization of Input) categories, as it involves improper handling of access control mechanisms and credential storage. The ATT&CK framework would classify this under T1547.001 (Registry Run Keys / Startup Folder) and T1068 (Local Privilege Escalation) as it affects system-level access controls and can lead to complete device lockout conditions. The vulnerability's classification as a local denial of service means it primarily affects the device's usability rather than creating remote access points, but the impact on user productivity and device functionality is substantial.
Mitigation strategies for CVE-2020-0469 should focus on implementing proper credential management procedures and ensuring that all synthetic password handling logic is thoroughly tested and validated. Android device manufacturers and system administrators should prioritize updating affected Android 11 devices with the latest security patches. The vulnerability highlights the importance of proper input validation and credential storage mechanisms within mobile operating systems. Users should be advised to maintain multiple backup access methods and to keep their devices updated with the latest security patches. Additionally, system administrators should monitor for any signs of credential loss or access denial conditions that may indicate exploitation of this vulnerability. The fix for this vulnerability typically involves correcting the logic error in the addEscrowToken method to ensure proper storage and handling of synthetic passwords within the lock settings service framework.