willitmerge is a command line tool to check if pull requests are mergeable. In versions 0.2.1 and prior, there is a command Injection vulnerability in willitmerge. The vulnerability manifests in this package due to the use of insecure child process execution API (exec) to which it concatenates user input, whether provided to the command-line flag, or is in user control in the target repository. At time of publication, no known fix is public.

Affected: npm: willitmerge

willitmerge describes itself as a command line tool to check if pull requests are mergeable. There is a Command Injection vulnerability in version `willitmerge@0.2.1`.

Resources: * Project's GitHub source code: https://github.com/shama/willitmerge/ * Project's npm package: https://www.npmjs.com/package/willitmerge

## Background on exploitation

Reporting a Command Injection vulnerability in `willitmerge` npm package.

A security vulnerability manifests in this package due to the use of insecure child process execution API (`exec`) to which it concateanes user input, whether provided to the command-line flag, or is in user control in the target repository.

## Exploit

### POC 1

1. Install `willitmerge` 2. Run it with the following command

```sh willitmerge --verbose --remote "https://github.com/lirantal/npq.git; touch /tmp/hel" ```

3. Confirm the file `/tmp/hel` is created on disk

### GitHub-sourced attack vector

[Lines 189-197](https://github.com/shama/willitmerge/blob/2fe91d05191fb05ac6da685828d109a3a5885028/lib/willitmerge.js#L189-L197) in `lib/willitmerge.js` pass user input controlled by repository collaborators into the git command:

```js var cmds = [ 'git checkout -b ' + branch + ' ' + that.options.remote + '/' + iss.base.ref, 'git remote add ' + branch + ' ' + gitUrl, 'git pull ' + branch + ' ' + iss.head.ref, 'git reset --merge HEAD', 'git checkout ' + origBranch, 'git branch -D ' + branch, 'git remote rm ' + branch ]; ```…