CVE-2016-3759 in Android
Summary
by MITRE
The Framework APIs in Android 5.0.x before 5.0.2, 5.1.x before 5.1.1, and 6.x before 2016-07-01 allow attackers to read backup data via a crafted application that leverages priv-app access to insert a backup transport, aka internal bug 28406080.
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Analysis
by VulDB Data Team • 02/22/2019
The vulnerability identified as CVE-2016-3759 represents a critical security flaw in the Android framework APIs that affected multiple versions of the operating system including Android 5.0.x before 5.0.2, 5.1.x before 5.1.1, and 6.x before the 2016-07-01 security update. This vulnerability resides in the backup and restore functionality of Android, specifically within the framework APIs that govern how applications interact with the system's backup mechanisms. The flaw stems from insufficient access controls and validation mechanisms that allow malicious applications to exploit their privileges within the system's application hierarchy. The vulnerability is particularly concerning because it leverages the privileged access that priv-app applications possess, which are system applications installed with elevated permissions that have access to sensitive system components and APIs.
The technical exploitation of this vulnerability occurs through a crafted application that takes advantage of the priv-app access rights to insert a custom backup transport component into the Android system. This backup transport is essentially a mechanism that handles the transfer of application data to and from backup storage, and when manipulated by an attacker, it provides unauthorized access to backup data that should remain protected. The flaw allows attackers to bypass normal access controls that would typically prevent applications from reading backup data belonging to other applications or system components. This represents a direct violation of Android's security model where applications should not be able to access each other's backup data without proper authorization. The vulnerability falls under the CWE-284 access control weakness category, specifically related to improper privileges for a resource, and aligns with ATT&CK technique T1218 which involves legitimate system tools and utilities to gain access to sensitive data.
The operational impact of this vulnerability is significant as it enables attackers to perform unauthorized data exfiltration from Android devices, potentially accessing sensitive information stored in backup files including personal data, credentials, application-specific information, and other confidential data that users expect to be protected. The vulnerability affects the integrity and confidentiality of the Android backup system, which is a fundamental security component designed to protect user data. Attackers could leverage this vulnerability to extract data from applications that have backup capabilities, including system applications that might contain sensitive information or credentials. The attack vector is particularly dangerous because it requires only a priv-app level of access, which can be achieved through various means including system-level compromise or exploitation of other vulnerabilities that allow privilege escalation. This vulnerability essentially undermines the backup system's security guarantees and represents a serious breach in Android's data protection mechanisms.
Mitigation strategies for this vulnerability include applying the security patches released by Google for the affected Android versions, which typically involve strengthening access controls for backup transport components and implementing proper validation of backup transport installations. Organizations should ensure that all Android devices are updated to the latest security patches and that the system applications are properly maintained to prevent unauthorized modifications. Users should be cautious about installing applications that may attempt to modify system components or install backup transports, and should verify the legitimacy and security of applications before installation. System administrators should monitor for any unauthorized modifications to system applications and implement proper application whitelisting policies. The vulnerability also highlights the importance of maintaining proper privilege separation within Android's application model, ensuring that applications with elevated privileges cannot access or manipulate backup mechanisms without proper authorization. Additionally, security monitoring should include detection of suspicious backup transport installations and access patterns that may indicate exploitation attempts. This vulnerability underscores the critical need for robust access control mechanisms and proper security validation in system APIs, particularly those that handle sensitive data operations.