Vitest Browser: Exposed Browser Mode API Can Proxy CDP and Overwrite Config Files, Leading to RCE
Date: 2026-06
Affected: npm/vite-plus, npm/@vitest/browser, npm/@vitest/browser
Attack vector: rce
Category: vulnerability-disclosure
Severity: Critical
CVE: CVE-2026-53633
CWE: CWE-749
CWE-862
CVSS: 9.8 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H)

## Summary Vitest Browser Mode exposes a `cdp()` API that forwards raw Chrome DevTools Protocol (CDP) methods over the Vitest browser WebSocket RPC. CDP is not gated by `browser.api.allowWrite`, `browser.api.allowExec`, `api.allowWrite`, or `api.allowExec`. As a result, disabling Browser Mode write and exec operations does not prevent a browser API client from using CDP to perform equivalent actions. In a verified reproduction with `allowWrite: false` and `allowExec: false`, CDP `Page.setDownloadBehavior` set the browser download directory to the project root, and CDP `Runtime.evaluate` downloaded a controlled `vite.config.ts`. Vitest reloaded the changed config and executed attacker-controlled Node.js code. When the Browser Mode API is also exposed to the network, this becomes remotely exploitable because the generated browser runner page exposes the API token, active session id, project name, and project root path needed to connect to the browser WebSocket API and select the target download directory. ## Impact This affects Browser Mode projects using a CDP-capable provider, such as Playwright Chromium, when the browser API server is exposed to the network, for example with `--browser.api.host=0.0.0.0`. In this mode Vitest warns that write and exec operations are disabled by default, but the generated browser runner page exposes enough metadata for a remote client to authenticate to the browser WebSocket API while an active session exists. This includes the browser AP


Mitigations:

Architectural layers (MAESTRO):