CVE-2019-5451 in App
Summary
by MITRE
Bypass lock protection in the Nextcloud Android app prior to version 3.6.1 allows accessing the files when repeatedly opening and closing the app in a very short time.
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Analysis
by VulDB Data Team • 11/14/2023
The vulnerability described in CVE-2019-5451 represents a critical security flaw in the Nextcloud Android application that undermines the fundamental authentication and authorization mechanisms designed to protect user data. This issue specifically affects versions of the Nextcloud mobile client prior to 3.6.1, where the application fails to properly enforce lock screen protection mechanisms during rapid application lifecycle transitions. The flaw exploits a race condition or improper state management within the mobile application's security framework, allowing unauthorized access to encrypted files and sensitive data stored within the application's protected environment.
The technical implementation of this vulnerability stems from inadequate session management and lock screen enforcement logic within the Android application's codebase. When users repeatedly open and close the Nextcloud app in rapid succession, the application fails to properly validate authentication state or enforce the configured lock screen protection settings. This behavior creates a temporal window where the application's security controls are bypassed, effectively allowing an attacker to access files without proper authentication. The vulnerability can be categorized under CWE-613, which addresses insufficient session expiration, and potentially CWE-306, which deals with missing authentication checks. The flaw demonstrates a failure in the application's security model to maintain consistent authentication state across application lifecycle events, particularly during foreground and background transitions.
From an operational perspective, this vulnerability poses significant risks to organizations and individual users who rely on Nextcloud for secure file storage and synchronization. The ability to bypass lock protection through simple rapid app opening and closing operations means that sensitive corporate data, personal documents, and confidential information could be accessed by unauthorized individuals who gain physical access to the device. This threat is particularly concerning in enterprise environments where mobile devices may be lost, stolen, or accessed by unauthorized personnel. The vulnerability essentially undermines the device's security posture by creating a persistent backdoor that can be exploited without requiring sophisticated attack techniques or network access. The ATT&CK framework categorizes this type of vulnerability under T1550.002, which involves use of stolen credentials, as the bypass effectively allows unauthorized access to protected resources through exploitation of local application security controls.
The mitigation strategy for CVE-2019-5451 requires immediate deployment of the Nextcloud Android app version 3.6.1 or later, which includes proper session management and lock screen enforcement mechanisms. Organizations should implement comprehensive mobile device management policies that enforce automatic lock screen activation after brief periods of inactivity and ensure proper application lifecycle handling. Security administrators should also conduct regular vulnerability assessments of mobile applications and establish monitoring procedures to detect potential exploitation attempts. The fix addresses the root cause by implementing proper state validation during application transitions and ensuring that lock screen protection mechanisms remain active regardless of how frequently the application is opened and closed. Additionally, users should be educated about the importance of maintaining up-to-date applications and the risks associated with using vulnerable versions of mobile security tools.