CVE-2018-5181 in Firefox
Summary
by MITRE
If a URL using the "file:" protocol is dragged and dropped onto an open tab that is running in a different child process the tab will open a local file corresponding to the dropped URL, contrary to policy. One way to make the target tab open more reliably in a separate process is to open it with the "noopener" keyword. This vulnerability affects Firefox < 60.
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Analysis
by VulDB Data Team • 07/20/2024
This vulnerability represents a critical cross-process access control flaw in the Firefox web browser that exploits the interaction between drag and drop operations and process isolation mechanisms. The issue arises when a malicious user constructs a URL using the file protocol and drags it onto an existing browser tab that operates in a separate child process. Under normal circumstances, Firefox employs process isolation to prevent tabs from accessing local resources directly, but this vulnerability allows bypassing those security boundaries. The flaw specifically affects versions prior to Firefox 60 where the browser's security model failed to properly enforce process separation during drag and drop operations involving file protocol URLs.
The technical implementation of this vulnerability exploits the fundamental principle of browser security where different tabs should operate in isolated processes to prevent privilege escalation and information leakage. When a file protocol URL is dropped onto a tab in a different process, the browser incorrectly interprets this action as a legitimate request to access local resources, bypassing the normal security checks that should prevent such cross-process file access. This behavior violates the security model that separates user browsing contexts from local file system access, effectively creating a path for malicious actors to potentially read arbitrary local files. The vulnerability is particularly concerning because it leverages legitimate browser functionality to achieve unauthorized access, making it difficult to detect through traditional security monitoring.
The operational impact of this vulnerability extends beyond simple file access, as it represents a potential vector for privilege escalation and information disclosure attacks. Attackers could craft malicious URLs that, when dropped onto targeted browser tabs, could reveal sensitive local files, system information, or user data. The fact that this vulnerability can be triggered through user interaction makes it particularly dangerous in phishing or social engineering scenarios where users might inadvertently drag and drop malicious URLs. The effectiveness of this attack is enhanced by the fact that the target tab can be made to run in a separate process using the "noopener" keyword, which is commonly used to prevent tab hijacking but inadvertently creates the conditions for this vulnerability to manifest.
Mitigation strategies for this vulnerability require both immediate patching and operational security improvements. The most effective solution is upgrading to Firefox version 60 or later where the security model has been properly implemented to prevent cross-process file access through drag and drop operations. Organizations should also implement security awareness training to prevent users from inadvertently dragging and dropping unknown URLs onto browser tabs. Additionally, browser hardening measures such as disabling drag and drop functionality for file protocol URLs or implementing stricter process isolation policies can provide additional defense in depth. This vulnerability aligns with CWE-276 which addresses improper permissions and access control, and relates to ATT&CK technique T1059 which covers command and scripting interpreter usage, as attackers could leverage this flaw to execute arbitrary file access operations.
The vulnerability demonstrates the complexity of modern browser security models where legitimate features can create unexpected attack surfaces. It highlights the importance of thorough security testing for interactions between different browser components and the need for comprehensive security reviews of user interface elements that can trigger underlying system operations. This flaw also underscores the challenges in maintaining process isolation when browsers must support rich interaction patterns like drag and drop, where the security boundaries become blurred between user interface operations and system-level access. Organizations should regularly audit their browser security configurations and maintain up-to-date patch management processes to prevent exploitation of such vulnerabilities that could compromise user data and system integrity.