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May 14, 2024

GHSL-2024-038: GitHub Actions expression injection in Kolibri

Jorge Rosillo

Coordinated Disclosure Timeline

Summary

Kolibri is vulnerable to Actions expression injection allowing an attacker to alter the repository and steal secrets.

Project

Kolibri

Tested Version

v0.16.0

Details

Actions expression injection in notify_team_new_comment.yml (GHSL-2024-038)

The notify_team_new_comment.yml workflow is triggered on issue_comment (i.e., when a when a comment inside an Issue or Pull Request is created). The workflow starts with full write-permissions GitHub repository token since the default workflow permissions on Organization/Repository level are set to read-write.

Taking the above into account, this workflow injects data controlled by said Issue (${{ github.event.issue.title }} – the title of the Issue) into a Run step’s script, allowing an attacker to take over the GitHub Runner to run custom commands and alter the repository.

- name: Escape title double quotes
  id: escape_title
  run: |
    title='${{ github.event.issue.title }}'
    echo "ISSUE_TITLE=${title//\"/\\\"}" >> "$GITHUB_OUTPUT"

This issue was found using CodeQL for JavaScript’s Expression injection in Actions query.

Impact

This issue may lead to stealing workflow secrets and modification of the repository.

Proof of Concept

  1. Open an Issue with the following title: '$(whoami)'
  2. Check the workflow runs for the new Actions run that will execute the command whoami.

Resources

Credit

This issue was discovered and reported by GHSL team member @jorgectf (Jorge Rosillo).

Contact

You can contact the GHSL team at securitylab@github.com, please include a reference to GHSL-2024-038 in any communication regarding this issue.