Coordinated Disclosure Timeline
- 2020-11-23: Report sent to maintainer
- 2020-11-23: Maintainer acknowledges
- 2020-11-24: Issue resolved
Summary
The ‘test_build_deploy.yml’ GitHub workflow is vulnerable to arbitrary command injection.
Product
wireapp/wire-webapp GitHub repository
Tested Version
Details
Issue: The title of public GitHub pull request and last commit message are used to format a shell command
A Pull Request title is used to format a bash script:
on:
...
pull_request:
branches: [master, dev, edge, avs]
...
- name: Set environment variables
run: |
...
echo "PR_LAST_COMMIT_MESSAGE=$(git log --format=%B -n 1 ${{github.event.after}} | head -n 1)" >> $GITHUB_ENV
...
- name: Set TITLE
run: echo "TITLE=${{github.event.pull_request.title || env.PR_LAST_COMMIT_MESSAGE}}" >> $GITHUB_ENV
...
Impact
This vulnerability allows for arbitrary command injection into the bash script. For a proof a concept a Pull Request with the following title title"; sleep 10 # will delay the action by ten seconds.
Workflows triggered by pull_request have limited repository token and no access to secrets. The attacker couldn’t do much except CI DoS attacks or running their own code in the context of the GitHub action runner.
Credit
This issue was discovered and reported by GHSL team member @JarLob (Jaroslav Lobačevski).
Contact
You can contact the GHSL team at securitylab@github.com, please include a reference to GHSL-2020-232 in any communication regarding this issue.