CVE-2023-28646 in App
Summary
by MITRE • 03/30/2023
Nextcloud android is an android app for interfacing with the nextcloud home server ecosystem. In versions from 3.7.0 and before 3.24.1 an attacker that has access to the unlocked physical device can bypass the Nextcloud Android Pin/passcode protection via a thirdparty app. This allows to see meta information like sharer, sharees and activity of files. It is recommended that the Nextcloud Android app is upgraded to 3.24.1. There are no known workarounds for this vulnerability.
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Analysis
by VulDB Data Team • 04/21/2023
The vulnerability identified as CVE-2023-28646 affects the Nextcloud Android application, specifically versions ranging from 3.7.0 through 3.24.0, presenting a critical security flaw that undermines the application's built-in protection mechanisms. This weakness manifests when an attacker gains access to an unlocked physical device, enabling them to circumvent the PIN or passcode security measures that are designed to protect sensitive data within the Nextcloud ecosystem. The vulnerability represents a significant compromise of user privacy and data integrity, as it allows unauthorized access to metadata associated with shared files, including information about file sharers, sharees, and user activities. The Nextcloud Android application serves as a primary interface for users to interact with their home server environment, making this vulnerability particularly concerning for individuals who store sensitive personal or professional information within their Nextcloud instances.
The technical flaw underlying CVE-2023-28646 stems from insufficient implementation of device-level security controls within the application's authentication framework. When a user sets up a PIN or passcode protection on their Nextcloud Android application, the system should create a secure barrier that prevents unauthorized access to the application's functionality and data even when the device is unlocked. However, this vulnerability demonstrates that a third-party application can exploit specific application programming interfaces or system-level access points to bypass these protections entirely. The flaw likely involves improper handling of application lifecycle events, insufficient validation of authentication states, or vulnerable inter-process communication mechanisms that allow malicious applications to gain access to protected application resources. This weakness specifically affects the application's ability to maintain a secure session state and enforce proper access controls, creating a pathway for data leakage that violates fundamental security principles of mobile application design.
The operational impact of this vulnerability extends beyond simple data exposure, as it fundamentally undermines the trust model that users place in their Nextcloud installations. When an attacker can bypass PIN protection, they gain access to detailed metadata about file sharing activities, which could reveal sensitive information about user behavior, collaboration patterns, and data relationships within the organization. This metadata exposure poses significant risks for both individual users and enterprises that rely on Nextcloud for document management and collaboration, as it can provide attackers with intelligence about network topology, user roles, and data access patterns. The vulnerability is particularly dangerous in environments where Nextcloud is used for sensitive business documents, healthcare records, or other regulated information where unauthorized access could result in compliance violations, financial losses, or reputational damage. The fact that no known workarounds exist for this vulnerability means that users must rely entirely on upgrading to the patched version, creating a window of exposure that could be exploited by threat actors with physical access to devices.
Organizations and individuals should immediately implement the recommended upgrade to Nextcloud Android version 3.24.1 to remediate this vulnerability, as this represents the only effective mitigation strategy available. The vulnerability aligns with CWE-613, which addresses insufficient session management, and demonstrates characteristics consistent with ATT&CK technique T1550.001 for legitimate credentials, as it allows unauthorized access through compromised device-level authentication mechanisms. Security teams should also consider implementing additional device security measures such as full-disk encryption, secure boot configurations, and mobile device management policies that can provide additional layers of protection. The vulnerability highlights the importance of robust application security testing, particularly for mobile applications that handle sensitive data and rely on device-level security features. Organizations should conduct thorough assessments of their mobile security posture, including evaluating the security of third-party applications installed on devices that may interact with sensitive enterprise data, and ensure that all endpoints are properly updated and monitored for similar vulnerabilities.