VPC Without Attached Subnet

• Query id: 3b3b4411-ad1f-40e7-b257-a78a6bb9673a
• Query name: VPC Without Attached Subnet
• Platform: CloudFormation
• Severity: Low
• Category: Resource Management
• CWE: 665
• URL: Github

Description

VPCs without attached subnets may indicate that they are not being used
Documentation

Code samples

Code samples with security vulnerabilities

Positive test num. 1 - yaml file

AWSTemplateFormatVersion: '2010-09-09'
Resources:
    myVPC_1:
      Type: AWS::EC2::VPC
      Properties:
        CidrBlock: 10.0.0.0/16
        EnableDnsSupport: 'false'
        EnableDnsHostnames: 'false'
        InstanceTenancy: dedicated

Positive test num. 2 - json file

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Resources": {
    "myVPC_1": {
      "Type": "AWS::EC2::VPC",
      "Properties": {
        "InstanceTenancy": "dedicated",
        "CidrBlock": "10.0.0.0/16",
        "EnableDnsSupport": "false",
        "EnableDnsHostnames": "false"
      }
    }
  }
}

Code samples without security vulnerabilities

Negative test num. 1 - yaml file

AWSTemplateFormatVersion: '2010-09-09'
Resources:
    myVPC_2:
      Type: AWS::EC2::VPC
      Properties:
        CidrBlock: 10.0.0.0/16
        EnableDnsSupport: 'false'
        EnableDnsHostnames: 'false'
        InstanceTenancy: dedicated
    mySubnet:
      Type: AWS::EC2::Subnet
      Properties:
        VpcId:
            Ref: myVPC_2
        CidrBlock: 10.0.0.0/24
        AvailabilityZone: "us-east-1a"

Negative test num. 2 - json file

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Resources": {
    "myVPC_2": {
      "Type": "AWS::EC2::VPC",
      "Properties": {
        "CidrBlock": "10.0.0.0/16",
        "EnableDnsSupport": "false",
        "EnableDnsHostnames": "false",
        "InstanceTenancy": "dedicated"
      }
    },
    "mySubnet": {
      "Type": "AWS::EC2::Subnet",
      "Properties": {
        "VpcId": {
          "Ref": "myVPC_2"
        },
        "CidrBlock": "10.0.0.0/24",
        "AvailabilityZone": "us-east-1a"
      }
    }
  }
}