CVE-2020-4075 in Electron
Summary
by MITRE
In Electron before versions 7.2.4, 8.2.4, and 9.0.0-beta21, arbitrary local file read is possible by defining unsafe window options on a child window opened via window.open. As a workaround, ensure you are calling `event.preventDefault()` on all new-window events where the `url` or `options` is not something you expect. This is fixed in versions 9.0.0-beta.21, 8.2.4 and 7.2.4.
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Analysis
by VulDB Data Team • 10/28/2020
The vulnerability described in CVE-2020-4075 represents a critical security flaw in the Electron framework that enables arbitrary local file read access through unsafe window options manipulation. This vulnerability affects Electron versions prior to 7.2.4, 8.2.4, and 9.0.0-beta21, making it a widespread issue across multiple major releases of the framework. The flaw stems from inadequate validation of window options when creating child windows through the window.open API, creating a pathway for malicious actors to access local file system resources without proper authorization. The vulnerability is classified under CWE-22 as Improper Limitation of a Pathname to a Restricted Directory, which specifically addresses issues where applications fail to properly restrict file system access to authorized directories. This weakness directly enables path traversal attacks that can be exploited to read sensitive files on the target system.
The technical implementation of this vulnerability occurs when developers fail to properly validate or sanitize the options parameter passed to window.open function calls. When a child window is created with unsafe options, particularly those containing file system paths or protocols, the Electron framework does not adequately restrict the access permissions that the newly created window can utilize. Attackers can leverage this by crafting malicious window.open calls that specify file:// URLs or other local file access mechanisms within the window options, effectively bypassing normal security boundaries that should prevent arbitrary file system access. This flaw operates at the application layer and can be exploited by malicious websites or applications that embed Electron-based components, making it particularly dangerous in web-to-desktop application contexts where user input might influence window creation parameters.
The operational impact of CVE-2020-4075 extends beyond simple file read capabilities to potentially expose sensitive system information, configuration files, user data, and application resources. Attackers could leverage this vulnerability to access personal files, application credentials, database files, or other sensitive information stored locally on the victim's system. The vulnerability also aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter: JavaScript, as exploitation typically involves JavaScript-based attacks that manipulate Electron's window creation API. The attack surface is particularly broad given that Electron is used by numerous applications including desktop browsers, development tools, and productivity applications, meaning that a successful exploitation could potentially affect thousands of applications across different platforms and use cases. Organizations using Electron-based applications are at risk of data breaches, information disclosure, and potential privilege escalation depending on the specific application context and user permissions.
The recommended mitigation strategy involves implementing proper event handling through the prevention of default window creation behavior for unexpected URLs or options. Developers should implement event.preventDefault() calls on all new-window events where the URL or options parameters do not match expected safe patterns. This approach aligns with the principle of least privilege and input validation, ensuring that only explicitly trusted window creation operations are allowed to proceed. The vulnerability fix released in versions 9.0.0-beta.21, 8.2.4, and 7.2.4 addresses the core issue by implementing proper validation of window options and strengthening the security boundaries around window creation operations. Organizations should also consider implementing additional security measures such as Content Security Policy (CSP) headers, regular security audits of Electron-based applications, and monitoring for unexpected window creation patterns. The fix demonstrates the importance of proper API design and security validation in cross-platform frameworks, particularly those that bridge web and native application environments, as highlighted in industry best practices for secure application development and the OWASP Top Ten security risks.