Schema of a JSON object has no properties defined

Average severity: Medium

Description

The schema for a JSON payload does not have any properties defined.

Example

The following is an example of how this type of risk could look in your API definition. The method defines the schema as the JSON payload NewPet. However, the actual content of that JSON object is not defined:

"post": {
  "description": "Creates a new pet in the store",
  "operationId": "addPet",
  "parameters": [
    {
      "name": "pet",
      "in": "body",
      "description": "pet to add to the system",
      "required": true,
      "schema": {
        "$ref": "#/definitions/NewPet"
      }
    }
  ]
}
...
"definitions": {
  "NewPet": {
    "type": "object",
    "description": "JSON defining a Pet object"
    }
  }
}

Possible exploit scenario

If you do not specify the types of the properties in the JSON payload, you effectively allow attackers to pass in any data. This opens your backend to various attacks, such as SQL injection.

This also lets attackers to try various unexpected inputs. Unexpected inputs may cause the backend server to crash or behave in an unexpected way. This in turn may cause the server to potentially leak stack trace that can be used for further attacks, or even data.

Remediation

Make sure you define the properties of JSON payloads. Here, the object NewPet has the properties name and tag defined:

"post": {
  "description": "Creates a new pet in the store",
  "operationId": "addPet",
  "parameters": [
    {
      "name": "pet",
      "in": "body",
      "description": "pet to add to the system",
      "required": true,
      "schema": {
        "$ref": "#/definitions/NewPet"
      }
    }
  ]
}
...
"definitions": {
  "NewPet": {
    "type": "object",
    "required": [
      "name"
    ],
    "properties": {
      "name": {
        "type": "string"
      },
      "tag": {
        "type": "string"
      }
    }
  }
}

 

 


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