CVE-2016-5279 in Firefox
Summary
by MITRE
Mozilla Firefox before 49.0 allows user-assisted remote attackers to obtain sensitive full-pathname information during a local-file drag-and-drop operation via crafted JavaScript code.
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Analysis
by VulDB Data Team • 09/20/2022
The vulnerability identified as CVE-2016-5279 represents a significant information disclosure flaw within Mozilla Firefox browsers prior to version 49.0. This security issue arises from the browser's handling of local file drag-and-drop operations, where malicious JavaScript code can exploit a weakness in the file system path resolution mechanism. The vulnerability specifically affects user-assisted remote attackers who can craft specialized JavaScript payloads to extract sensitive path information from the victim's local file system. The flaw exists in the browser's implementation of the drag-and-drop API when dealing with local file references, creating an unintended information leak that could reveal full file paths on the victim's system.
The technical mechanism behind this vulnerability involves the browser's processing of file objects during drag-and-drop operations. When users drag local files into Firefox, the browser's JavaScript engine handles these file references and exposes metadata including file paths to the executing JavaScript code. In affected versions, the implementation fails to properly sanitize or obscure these path details, allowing attackers to craft malicious scripts that can access and retrieve the complete directory structure information. This occurs because the browser's security model does not adequately restrict access to sensitive path information during the drag-and-drop interaction, particularly when JavaScript code is involved in handling the file objects. The vulnerability manifests when JavaScript code attempts to access properties of file objects that contain the full system path information, which should be restricted for security reasons.
The operational impact of this vulnerability extends beyond simple information disclosure, as the leaked path information could enable attackers to perform more sophisticated attacks. An attacker who successfully exploits this vulnerability can gather detailed knowledge about the victim's file system structure, including directory layouts and potentially sensitive file locations. This information can be leveraged for further exploitation attempts, such as targeting specific files or directories that might contain credentials, configuration data, or other sensitive information. The vulnerability is particularly concerning because it operates during legitimate user interactions with local files, making it difficult to detect and potentially allowing for covert information gathering without obvious user awareness. The attack requires user interaction through a crafted drag-and-drop operation, but once initiated, it can provide attackers with substantial path information that could facilitate additional security breaches.
This vulnerability maps to CWE-200, which covers "Information Exposure," and specifically relates to improper information handling during user interaction scenarios. The flaw demonstrates weaknesses in browser security boundaries and JavaScript execution environments, aligning with ATT&CK technique T1059.007 for JavaScript-based execution and T1082 for system information discovery. Organizations should prioritize updating to Firefox version 49.0 or later, which includes patches that properly sanitize file path information during drag-and-drop operations. Additional mitigations include implementing browser security policies that restrict file access permissions, monitoring for suspicious JavaScript behavior during file operations, and educating users about the risks of interacting with untrusted content. The vulnerability underscores the importance of proper input validation and output sanitization in web browser implementations, particularly when handling user-generated file references and system-level information access.