CVE-2016-3918 in Android
Summary
by MITRE
email/provider/AttachmentProvider.java in AOSP Mail in Android 4.x before 4.4.4, 5.0.x before 5.0.2, 5.1.x before 5.1.1, 6.x before 2016-10-01, and 7.0 before 2016-10-01 does not ensure that certain values are integers, which allows attackers to read arbitrary attachments via a crafted application that provides a pathname value, aka internal bug 30745403.
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Analysis
by VulDB Data Team • 09/22/2022
The vulnerability identified as CVE-2016-3918 affects the Android Open Source Project Mail application across multiple Android versions, specifically targeting Android 4.x before 4.4.4, 5.0.x before 5.0.2, 5.1.x before 5.1.1, 6.x before 2016-10-01, and 7.0 before 2016-10-01. This security flaw exists within the email/provider/AttachmentProvider.java component and represents a critical issue in input validation and type checking mechanisms. The vulnerability stems from the application's failure to properly validate that specific values are integers, creating a path traversal condition that can be exploited by malicious actors. The issue manifests through a crafted application that manipulates pathname values, allowing unauthorized access to arbitrary attachments stored on the device. This flaw directly impacts the integrity of the email application's security model and potentially exposes sensitive user data.
The technical implementation of this vulnerability resides in the AttachmentProvider.java file where the application processes attachment paths without proper type validation. When an application attempts to access email attachments, the system should validate that pathname parameters are indeed integers to prevent malicious input from being interpreted as file system paths. However, the absence of this validation allows attackers to craft malicious inputs that bypass normal access controls. The vulnerability specifically relates to improper input sanitization where integer values expected for path resolution are not properly validated, enabling attackers to manipulate the attachment retrieval process. This type of flaw aligns with CWE-190, Integer Overflow or Wraparound, and CWE-20, Improper Input Validation, as the system fails to properly validate integer parameters before processing them. The vulnerability creates a path traversal scenario where attackers can access files outside of the intended attachment directory through manipulation of pathname values.
The operational impact of CVE-2016-3918 is significant as it allows remote attackers to access arbitrary email attachments stored on affected Android devices. This creates a potential data breach scenario where sensitive information contained in email attachments could be accessed without proper authorization. The vulnerability affects users across multiple Android versions, making it particularly dangerous as it impacts a large user base. Attackers could exploit this weakness to access personal emails, business documents, financial records, or other sensitive attachments that users expect to remain private. The flaw essentially undermines the security boundaries of the email application, allowing unauthorized file system access that could lead to further exploitation. From an attacker's perspective, this vulnerability represents a low-effort, high-impact method for data exfiltration, particularly when combined with other attack vectors that might be available on the device.
Mitigation strategies for this vulnerability focus on immediate patching and system updates as the primary defense mechanism. Users should update their Android devices to versions that contain the security fixes for this vulnerability, particularly upgrading to Android 4.4.4, 5.0.2, 5.1.1, or the appropriate security patch release for Android 6.0 and 7.0. System administrators should ensure that enterprise devices are updated promptly to prevent potential data breaches within organizational networks. The vulnerability also highlights the importance of proper input validation in mobile applications, suggesting that developers implement robust type checking mechanisms for all parameters that influence file system access. Organizations should conduct security audits of their mobile applications to identify similar input validation flaws that could create similar vulnerabilities. From the ATT&CK framework perspective, this vulnerability maps to T1059 Command and Scripting Interpreter and T1566 Phishing, as attackers could leverage this weakness to access sensitive attachments and potentially use the information for further social engineering attacks. The vulnerability also demonstrates the importance of defense in depth principles where multiple layers of security controls should be implemented to prevent unauthorized access to sensitive data.