CVE-2016-5265 in Firefox
Summary
by MITRE
Mozilla Firefox before 48.0 and Firefox ESR 45.x before 45.3 allow user-assisted remote attackers to bypass the Same Origin Policy, and conduct Universal XSS (UXSS) attacks or read arbitrary files, by arranging for the presence of a crafted HTML document and a crafted shortcut file in the same local directory.
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Analysis
by VulDB Data Team • 09/09/2022
The vulnerability identified as CVE-2016-5265 represents a critical security flaw in Mozilla Firefox versions prior to 48.0 and Firefox ESR 45.x versions prior to 45.3. This vulnerability specifically targets the browser's Same Origin Policy implementation, which serves as a fundamental security mechanism designed to prevent unauthorized access to resources across different origins. The flaw enables attackers to bypass these critical security boundaries through a sophisticated attack vector involving the manipulation of local file systems and HTML document structures. The vulnerability operates under the Common Weakness Enumeration classification of CWE-20, which encompasses Improper Input Validation, and falls within the ATT&CK framework's technique T1059 for Command and Scripting Interpreter, specifically focusing on the abuse of local file system interactions.
The technical exploitation of this vulnerability requires a precise sequence of conditions to be met, involving the deliberate placement of both a crafted HTML document and a specially constructed shortcut file within the same local directory. This attack methodology leverages the browser's handling of local file references and its interaction with the operating system's file system APIs. When Firefox processes these specific file combinations, it fails to properly validate the origins of referenced resources, allowing malicious code execution that circumvents the browser's security model. The vulnerability specifically enables Universal Cross-Site Scripting (UXSS) attacks, where malicious scripts can execute in the context of any origin, and also permits arbitrary file reading capabilities that can access sensitive local data. The attack requires user interaction to place these malicious files in the targeted directory, making it a user-assisted remote attack rather than a fully automated exploit.
The operational impact of CVE-2016-5265 extends beyond simple privilege escalation or data theft, as it fundamentally undermines the browser's security architecture. Successful exploitation allows attackers to bypass the Same Origin Policy, which is one of the most critical security controls in web browsers. This enables attackers to perform actions such as reading arbitrary files from the local file system, executing malicious code across different origins, and potentially accessing sensitive information that should remain isolated. The vulnerability creates a persistent security risk that can be exploited repeatedly, as long as the attacker can influence the user to interact with malicious files. Organizations using affected Firefox versions face significant risk of data breaches, privilege escalation attacks, and potential lateral movement within their networks through the exploitation of this vulnerability.
Mitigation strategies for CVE-2016-5265 focus primarily on immediate remediation through software updates to Firefox versions 48.0 and 45.3 respectively, which address the underlying Same Origin Policy bypass mechanism. System administrators should prioritize patching affected installations and implementing comprehensive browser security policies that restrict file system access permissions. Additional protective measures include deploying application whitelisting solutions, implementing strict file system access controls, and conducting regular security assessments of browser configurations. The vulnerability highlights the importance of maintaining up-to-date software versions and demonstrates the critical need for continuous security monitoring and vulnerability management programs. Organizations should also consider implementing network-based intrusion detection systems that can identify suspicious file access patterns and potential exploitation attempts related to local file system interactions. Security teams must ensure that user education programs emphasize the dangers of interacting with untrusted files in local directories, as the attack requires user-assisted execution to be effective.