EC2 Instance Public IP

What this rule checks

Detects EC2 instances whose NetworkInterfaces specify AssociatePublicIpAddress=true, exposing the instance directly to the internet.

How to fix it

1. 1Set AssociatePublicIpAddress to false on the NetworkInterface
2. 2Place the instance in a private subnet and use a NAT Gateway / VPC endpoint for outbound
3. 3Use an ALB / NLB in a public subnet to front the workload instead

import { aws_ec2 as ec2 } from 'aws-cdk-lib';

const vpc = new ec2.Vpc(this, 'Vpc');

new ec2.Instance(this, 'Instance', {
  vpc,
  vpcSubnets: { subnetType: ec2.SubnetType.PUBLIC },
  instanceType: ec2.InstanceType.of(ec2.InstanceClass.T3, ec2.InstanceSize.MICRO),
  machineImage: ec2.MachineImage.latestAmazonLinux2023(),
  associatePublicIpAddress: true,
});

import { aws_ec2 as ec2 } from 'aws-cdk-lib';

const vpc = new ec2.Vpc(this, 'Vpc');

new ec2.Instance(this, 'Instance', {
  vpc,
  vpcSubnets: { subnetType: ec2.SubnetType.PRIVATE_WITH_EGRESS },
  instanceType: ec2.InstanceType.of(ec2.InstanceClass.T3, ec2.InstanceSize.MICRO),
  machineImage: ec2.MachineImage.latestAmazonLinux2023(),
  associatePublicIpAddress: false,
});

CDK Insights pinpoints the exact file and line in your CDK source for every finding, so you can jump straight to the fix.

Affected resource types

Intentional? Suppress this finding

Sometimes a flag is deliberate — a genuinely public endpoint, say. You can dismiss ec2-instance-public-ip and the reason is kept in the report, not silently hidden.

In .cdk-insights.json:

{
  "ignoreRules": [
    { "id": "ec2-instance-public-ip", "reason": "Why this is intentional" }
  ]
}

Or inline in your CDK code:

Validations.of(scope).acknowledge({
  id: 'cdk-insights::ec2-instance-public-ip',
  reason: 'Why this is intentional',
});

Use the rule ID ec2-instance-public-ip shown above — not the CDK-* ID from SARIF / GitHub code scanning. To dismiss every finding on one construct instead, use ignorePaths. Suppression docs →

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