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Electron is a popular framework for building cross-platform desktop applications using JavaScript, HTML, and CSS. One of its key security features is context isolation, which separates the preload script’s privileged execution environment from the untrusted web content loaded in a renderer process. To safely expose selected APIs from the preload world to the web page, developers use the `contextBridge` module. This module allows explicit, controlled exposure of functions and objects, ensuring that the web content cannot directly access Node.js or internal Electron capabilities.
The vulnerability identified as CVE-2026-70601 arises from a subtle interaction between `contextBridge` and JavaScript’s Function.prototype.bind. When an application exposes a Promise-returning function via contextBridge—a standard pattern often used to wrap `ipcRenderer.invoke` for communication between the renderer and main process—an attacker who can execute JavaScript in the main world (e.g., via cross-site scripting) can hijack the `bind` method of that function. By replacing or manipulating Function.prototype.bind, the attacker can intercept the function’s invocation and alter its behavior or context.
This hijack effectively breaks the isolation provided by contextBridge. Instead of the function executing in the intended preload context, the attacker can force it to run in the main world, or they can gain a reference to the function’s internal `[
]` and other properties. Through this, the attacker obtains direct access to the preload world and, consequently, every capability that the preload script possesses. If the renderer is not sandboxed or if `nodeIntegration` is enabled, this escalation can lead to full Node.js access, allowing the attacker to execute arbitrary system commands, read and write files, and compromise the entire application. The flaw affects any Electron application that loads untrusted content in a window where `contextBridge` is used to expose Promise-returning functions. This includes the vast majority of Electron apps that follow the recommended practice of using `contextBridge` for secure IPC. The vulnerability is present in all Electron versions prior to 39.8.9, 40.9.2, 41.2.2, and 42.0.0-beta.5. It was discovered and reported through the Electron security program, and patches were released on August 5, 2026. There are no effective application-side workarounds; the only mitigation is to update to a patched Electron version. The issue is classified as high severity due to the potential for complete compromise of the application and the host system. <h2 style="color: blue;">DailyCVE Form:</h2> Platform: Electron Version: Multiple affected Vulnerability: Context isolation bypass Severity: High date: 2026-08-05 <h2 style="color: blue;">Prediction: Patch already available</h2> <h2 style="color: blue;">What Undercode Say:</h2> [bash] Check Electron version in a project npm list electron Or globally electron --version Update Electron to a patched version npm install [email protected] or npm install [email protected] or npm install [email protected] or npm install [email protected]
// Example of vulnerable pattern
const { contextBridge, ipcRenderer } = require('electron');
contextBridge.exposeInMainWorld('api', {
// This Promise-returning function is vulnerable
sendMessage: (msg) => ipcRenderer.invoke('send-message', msg)
});
Exploit:
An attacker with JavaScript execution in the main world (e.g., via XSS) can overwrite `Function.prototype.bind` before invoking the exposed function. By supplying a custom `bind` implementation, the attacker can capture the target function reference and execute it in the main world context, bypassing `contextBridge` isolation. This grants access to the preload script’s environment, including any Node.js modules or Electron APIs exposed there. From this point, the attacker can perform privileged operations such as reading local files, spawning child processes, or making arbitrary IPC calls.
Protection:
Upgrade to a patched Electron version immediately. There is no other mitigation. Ensure that `contextIsolation` is enabled and `nodeIntegration` is disabled in all renderer processes that load untrusted content. Regularly audit the functions exposed via `contextBridge` and avoid exposing functions that return Promises if they are not strictly necessary. Monitor for any unexpected modifications to built-in prototypes like `Function.prototype` in the main world.
Impact:
Successful exploitation allows an attacker to bypass Electron’s context isolation mechanism. In renderers without a sandbox or with `nodeIntegration` enabled, this leads to full Node.js access, enabling arbitrary code execution, file system manipulation, network access, and complete compromise of the application and the user’s system. Even in sandboxed renderers, the attacker gains the full capabilities of the preload script, which often include sensitive IPC channels and internal application logic. The vulnerability undermines the security model of Electron applications that rely on `contextBridge` to safely interact with untrusted content.
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Sources:
Reported By: github.com
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