S3 Bucket Policy Grants Public Read

What this rule checks

Detects S3 bucket policies that allow object reads to a wildcard principal with no scoping condition — the bucket contents are publicly downloadable.

How to fix it

1. 1Serve public content through CloudFront with Origin Access Control and scope the bucket policy to the distribution
2. 2For genuinely public datasets, suppress this rule on the bucket policy to record the decision

import * as s3 from 'aws-cdk-lib/aws-s3';

const bucket = new s3.Bucket(this, 'Assets');

new s3.CfnBucketPolicy(this, 'Policy', {
  bucket: bucket.bucketName,
  policyDocument: {
    Version: '2012-10-17',
    Statement: [
      {
        Effect: 'Allow',
        Principal: '*',
        Action: 's3:GetObject',
        Resource: bucket.arnForObjects('*'),
      },
    ],
  },
});

import * as s3 from 'aws-cdk-lib/aws-s3';

const bucket = new s3.Bucket(this, 'Assets');

new s3.CfnBucketPolicy(this, 'Policy', {
  bucket: bucket.bucketName,
  policyDocument: {
    Version: '2012-10-17',
    Statement: [
      {
        Effect: 'Allow',
        Principal: { Service: 'cloudfront.amazonaws.com' },
        Action: 's3:GetObject',
        Resource: bucket.arnForObjects('*'),
        Condition: {
          StringEquals: {
            'aws:SourceArn':
              'arn:aws:cloudfront::111122223333:distribution/EDFDVBD6EXAMPLE',
          },
        },
      },
    ],
  },
});

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 s3-bucket-policy-public-read and the reason is kept in the report, not silently hidden.

In .cdk-insights.json:

{
  "ignoreRules": [
    { "id": "s3-bucket-policy-public-read", "reason": "Why this is intentional" }
  ]
}

Or inline in your CDK code:

Validations.of(scope).acknowledge({
  id: 'cdk-insights::s3-bucket-policy-public-read',
  reason: 'Why this is intentional',
});

Use the rule ID s3-bucket-policy-public-read 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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