Identifying and Preventing Common CloudFormation Security Issues

Identifying and Preventing Common CloudFormation Security Issues

Public resource exposure represents one of the most common CloudFormation security issues. Templates might inadvertently create publicly accessible resources through misconfigured security groups, S3 bucket policies, or API Gateway settings. These misconfigurations often result from copying example templates without understanding security implications or using overly permissive defaults.

# Example of insecure CloudFormation template with common issues
AWSTemplateFormatVersion: '2010-09-09'
Description: 'Insecure template demonstrating common security issues'

Resources:
  # INSECURE: S3 bucket with public read access
  PublicBucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: my-public-data-bucket
      AccessControl: PublicRead  # Security Issue: Allows public access
      
  # INSECURE: RDS instance with public access
  DatabaseInstance:
    Type: AWS::RDS::DBInstance
    Properties:
      DBInstanceIdentifier: my-database
      Engine: mysql
      MasterUsername: admin
      MasterUserPassword: ChangeMePlease123!  # Security Issue: Hardcoded password
      DBInstanceClass: db.t3.micro
      AllocatedStorage: 20
      PubliclyAccessible: true  # Security Issue: Database exposed to internet
      
  # INSECURE: Security group with overly permissive rules
  WebServerSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Allow all traffic
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: 0
          ToPort: 65535
          CidrIp: 0.0.0.0/0  # Security Issue: Allows all inbound traffic

Hardcoded secrets in CloudFormation templates create severe security vulnerabilities. Templates containing passwords, API keys, or other sensitive data expose these secrets to anyone with template access. Even when templates are stored securely, AWS CloudTrail logs and CloudFormation event history might capture sensitive parameter values, creating additional exposure vectors.

IAM permission escalation through CloudFormation templates enables attackers to gain elevated privileges. Templates that create IAM roles or policies with excessive permissions can be exploited to escalate privileges beyond the template author's intended access. This risk increases when templates create roles that trust principals outside the organization's control.