ECR Mutable Image Tags

What this rule checks

Detects ECR repositories that allow image tags to be overwritten.

How to fix it

1. 1Set ImageTagMutability to IMMUTABLE

import { App, Stack } from 'aws-cdk-lib';
import { Construct } from 'constructs';
import * as ecr from 'aws-cdk-lib/aws-ecr';

// FLAGGED: ImageTagMutability defaults to MUTABLE.
new ecr.CfnRepository(this, 'Repo', {
  repositoryName: 'app',
  lifecyclePolicy: {
    lifecyclePolicyText: JSON.stringify({
      rules: [{ rulePriority: 1, selection: { tagStatus: 'untagged', countType: 'sinceImagePushed', countUnit: 'days', countNumber: 14 }, action: { type: 'expire' } }],
    }),
  },
});

import { App, Stack } from 'aws-cdk-lib';
import { Construct } from 'constructs';
import * as ecr from 'aws-cdk-lib/aws-ecr';

// FIXED: tags are immutable and cannot be overwritten.
new ecr.CfnRepository(this, 'Repo', {
  repositoryName: 'app',
  imageTagMutability: 'IMMUTABLE',
  lifecyclePolicy: {
    lifecyclePolicyText: JSON.stringify({
      rules: [{ rulePriority: 1, selection: { tagStatus: 'untagged', countType: 'sinceImagePushed', countUnit: 'days', countNumber: 14 }, action: { type: 'expire' } }],
    }),
  },
});

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 ecr-mutable-tags and the reason is kept in the report, not silently hidden.

In .cdk-insights.json:

{
  "ignoreRules": [
    { "id": "ecr-mutable-tags", "reason": "Why this is intentional" }
  ]
}

Or inline in your CDK code:

Validations.of(scope).acknowledge({
  id: 'cdk-insights::ecr-mutable-tags',
  reason: 'Why this is intentional',
});

Use the rule ID ecr-mutable-tags 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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