CVE-2019-11700 in Firefox
Summary
by MITRE
A hyperlink using the res: protocol can be used to open local files at a known location in Internet Explorer if a user approves execution when prompted. *Note: this issue only occurs on Windows. Other operating systems are unaffected.*. This vulnerability affects Firefox < 67.
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Analysis
by VulDB Data Team • 06/06/2024
The vulnerability identified as CVE-2019-11700 represents a critical security flaw in web browser implementations that allows for local file access through crafted hyperlinks. This issue specifically leverages the res protocol handler within Internet Explorer to bypass normal security boundaries and potentially access local system resources. The vulnerability is particularly concerning because it requires only user interaction to exploit, making it highly practical in real-world attack scenarios where social engineering can be employed to convince victims to click malicious links. The res protocol, typically used for referencing resources within applications, becomes a vector for privilege escalation when improperly validated by the browser's security model.
The technical implementation of this vulnerability stems from insufficient validation of URI schemes within Internet Explorer's processing pipeline. When a user encounters a hyperlink using the res: protocol, the browser fails to properly sanitize or restrict access to local file system resources, allowing the protocol handler to potentially open files at predetermined locations on the victim's system. This flaw operates at the application layer of the OSI model, specifically within the web browser's resource handling mechanism, and can be classified under CWE-22 as "Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')". The vulnerability's exploitation requires the user to approve execution when prompted, indicating that while the browser itself is the primary target, user interaction remains a necessary component for successful compromise.
The operational impact of CVE-2019-11700 extends beyond simple information disclosure to potentially enable more severe attacks including privilege escalation and system compromise. Attackers can craft malicious links that, when clicked, access sensitive local files such as configuration data, credential storage locations, or other system resources that may contain valuable information for further exploitation. The vulnerability's Windows-only nature means that attackers targeting enterprise environments with Internet Explorer as their primary browser face a significant attack surface. This aligns with ATT&CK technique T1059.001 for Command and Scripting Interpreter, where adversaries can leverage local file access to execute malicious code or gather intelligence. The impact is particularly severe in corporate environments where Internet Explorer remains in use, as it can provide attackers with access to internal network resources that should normally be protected by the browser's security sandbox.
Mitigation strategies for CVE-2019-11700 should focus on both immediate remediation and long-term architectural improvements. The primary recommendation involves updating affected systems to patched versions of Internet Explorer and Firefox, as Microsoft and Mozilla have released security updates addressing this specific vulnerability. Organizations should also implement network-level controls such as web application firewalls that can detect and block res protocol handlers in web traffic. Browser hardening measures including disabling or restricting protocol handlers, implementing strict content security policies, and deploying sandboxing technologies can significantly reduce the attack surface. Additionally, user education programs should emphasize the importance of verifying link origins and understanding the security implications of approving execution prompts, as this vulnerability demonstrates the critical role of social engineering in successful exploitation. The vulnerability's remediation also highlights the importance of adhering to secure coding practices and implementing proper input validation for all URI schemes within web applications and browsers.