Array schema with numeric items has no maximum defined

Average severity: Medium

Description

An array schema containing numeric items does not specify the maximum value of the items.

For more details, see the OpenAPI Specification.

Example

The following is an example of how this type of risk could look in your API definition. The array schema accepts items of the type integer but does not specify the maximum value for them:

"post": {
  "description": "Add a new lock combination",
  "operationId": "addCombo",
  "parameters": [
    {
      "name": "lockCombo",
      "in": "body",
      "description": "Lock combination to add to the list",
      "required": true,
      "schema": {
        "type": "object",
        "required": [
          "combination"
        ],
        "properties": {
        "combination": {
          "type": "array",
          "items": {
            "type": "integer"
          }
        }
      }
    }
   ],

Possible exploit scenario

If you do not limit the range of accepted values for numeric items in array schemas, attackers can try to send unexpected input to your backend server. This may cause the backend server to fail in an unexpected way and open the door to further attacks.

For example, the backend server could throw an exception and return a stack trace on the error. The trace could contain information on the exact software stack used in the implementation. This enables the attacker to launch an attack on specific vulnerabilities known in that stack.

Remediation

Set both the minimum and maximum values for numeric items in array schemas to limit the accepted values to the range that works for your application:

"post": {
  "description": "Add a new lock combination",
  "operationId": "addCombo",
  "parameters": [
    {
      "name": "lockCombo",
      "in": "body",
      "description": "Lock combination to add to the list",
      "required": true,
      "schema": {
        "type": "object",
        "required": [
          "name"
        ],
        "properties": {
        "combination": {
          "type": "array",
          "items": {
            "type": "integer",
            "minimum": 0,
            "maximum": 9
          }
        }
      }
    }
   ],

Get API Security news directly in your Inbox.

By clicking Subscribe you agree to our Data Policy