CVE-2017-8769 in WhatsApp Messenger
Summary
by MITRE
** DISPUTED ** Facebook WhatsApp Messenger 2.17.146 for Android uses the SD card for cleartext storage of files (Audio, Documents, Images, Video, and Voice Notes) associated with a chat, even after that chat is deleted. There may be users who expect file deletion to occur upon chat deletion, or who expect encryption (consistent with the application's use of an encrypted database to store chat text). NOTE: the vendor reportedly indicates that they do not "consider these to be security issues" because a user may legitimately want to preserve any file for use "in other apps like the Google Photos gallery" regardless of whether its associated chat is deleted.
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Analysis
by VulDB Data Team • 08/05/2024
The vulnerability described in CVE-2017-8769 pertains to Facebook WhatsApp Messenger version 2.17.146 for Android devices, where the application stores chat-associated media files in cleartext format on the device's SD card. This behavior manifests even after users delete chats, creating a potential privacy and security concern that has been disputed by the vendor. The flaw exists in the application's data management approach where files such as audio, documents, images, videos, and voice notes remain accessible on the SD card despite the deletion of their corresponding chat conversations. This discrepancy between user expectations and actual application behavior creates confusion regarding data persistence and privacy controls.
The technical implementation of this vulnerability stems from WhatsApp's decision to store media files in a location that bypasses the normal encryption mechanisms used for chat text data. While the application's database employs encryption for text messages, the media files are written to the SD card in plain text format without any encryption. This design choice creates a data exposure risk where sensitive information remains accessible to anyone with access to the device's SD card. The vulnerability aligns with CWE-312 (Cleartext Storage of Sensitive Information) which specifically addresses the storage of sensitive data in an unencrypted format that can be easily accessed by unauthorized parties.
From an operational perspective, this vulnerability presents significant privacy implications for users who may expect complete data deletion upon chat removal. The behavior contradicts user expectations of comprehensive privacy controls, as files that were once associated with deleted conversations remain accessible on the device. Attackers with physical access to the device or those who gain access to the SD card can potentially extract and analyze these media files, even after chat deletion. This creates a scenario where sensitive information might persist longer than intended, particularly in cases where users believe their data has been completely removed from the device. The vulnerability also impacts the principle of least privilege and data minimization, as unnecessary data remains accessible on the device.
The vendor's response to this issue, as indicated in the description, dismisses it as a non-security concern by stating that users may legitimately want to preserve files for use in other applications. This reasoning, however, overlooks the fundamental privacy expectations users have regarding data deletion and the potential for unintended data exposure. The vendor's position conflicts with standard security practices that emphasize user control over their data and the principle that deleted data should remain inaccessible. This vulnerability demonstrates how application design choices can create unexpected privacy implications that may not align with user expectations or industry security standards.
The implications of this vulnerability extend beyond simple data retention, as it affects the overall security posture of the application and user privacy. Users may unknowingly leave sensitive information accessible on their devices, particularly in scenarios where devices are lost or stolen, or when multiple users share a device. The lack of encryption for media files stored on the SD card creates a persistent data exposure risk that persists beyond the normal operational lifecycle of chat conversations. This behavior may also impact compliance with privacy regulations that require data minimization and proper data handling practices, potentially creating legal and regulatory concerns for organizations using WhatsApp for business communications.
Recommended mitigations for this vulnerability include implementing proper file deletion mechanisms that ensure complete removal of media files when chats are deleted, applying encryption to all stored media files regardless of their association with chat conversations, and providing users with clear information about data retention policies. Organizations should consider implementing additional security controls such as device encryption and access controls to protect against unauthorized access to SD card data. The vulnerability highlights the importance of maintaining consistency in security practices across all data storage mechanisms within applications, ensuring that encryption and access controls are applied uniformly to protect user privacy and prevent unintended data exposure.