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Insecure service configuration - Security Groups

Description​

EC2 Security Groups are not explicitly defined. Security Group input/output rules are not defined.

Impact​

  • Extract information from the server without proper consent.
  • Create holes to gain remote access.

Recommendation​

Securely configure the vulnerable service by explicitly defining the Security Groups.

Threat​

Anonymous attacker with access to an EC2 instance from an internal network.

Expected Remediation Time​

⌚ 30 minutes.

Score​

Default score using CVSS 3.1. It may change depending on the context of the vulnerability.

Base​

  • Attack vector: A
  • Attack complexity: H
  • Privileges required: N
  • User interaction: N
  • Scope: U
  • Confidentiality: L
  • Integrity: L
  • Availability: N

Temporal​

  • Exploit code madurity: P
  • Remediation level: O
  • Report confidence: C

Result​

  • Vector string: CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N/E:P/RL:O/RC:C
  • Score:
    • Base: 4.2
    • Temporal: 3.8
  • Severity:
    • Base: Medium
    • Temporal: Low

Code Examples​

Compliant code​

The services have specific security groups configured

Resources:
  MyLaunchTemplate2:
    Type: AWS::EC2::LaunchTemplate
    Properties:
      LaunchTemplateName: MyLaunchTemplate
      LaunchTemplateData:
        InstanceType: t2.micro
        KeyName: MyKeyPair
  MyEC2Instance:
    Type: AWS::EC2::Instance
    Properties:
      ImageId: "ami-79fd7eee"
      KeyName: "testkey"
      SecurityGroups:
        - name1

Non compliant code​

There are services with the default security groups configured

Resources:
  MyLaunchTemplate:
    Type: AWS::EC2::LaunchTemplate
    Properties:
      LaunchTemplateName: MyLaunchTemplate
      LaunchTemplateData:
        InstanceType: t2.micro
        KeyName: MyKeyPair
        SecurityGroupIds:
          - sg-083cd3bfb8example
  MyEC2Instance:
    Type: AWS::EC2::Instance
    Properties:
      ImageId: "ami-79fd7eee"
      KeyName: "testkey"

Using the AWS CLI, the following command checks if the EC2 instance uses the default security groups

$ aws ec2 describe-instances
      --region us-east-1
      --filters "Name=instance.group-name,Values=default"
      --output table
      --query 'Reservations[*].Instances[*].InstanceId'

If the output returns one or more instance ID, these have the default security group configured

Requirements​

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