A recent security vulnerability in the Amazon Web Services (AWS) Cloud Development Kit (CDK) has raised alarms about the potential for account takeovers. Researchers from Aqua disclosed that under specific circumstances, the flaw could allow attackers to gain administrative access to a target AWS account, leading to a complete account takeover. The issue primarily stems from predictable naming conventions for S3 buckets created during the CDK bootstrapping process. This vulnerability, identified through responsible disclosure on June 27, 2024, was promptly addressed in the CDK version 2.149.0 released in July.
The AWS CDK is an open-source framework that allows developers to define and provision cloud application resources using programming languages like Python, TypeScript, or JavaScript. During the bootstrapping process, the CDK automatically creates certain AWS resources, including S3 buckets and IAM roles. However, the default naming patterns for these resources often remain unchanged, making them predictable. This predictability enables attackers to engage in what’s known as S3 Bucket Namesquatting, where they can claim a bucket using a default name if it has been deleted, potentially leading to unauthorized access to sensitive data.
Once an attacker has claimed a bucket with a predictable name, they can exploit the situation to perform malicious actions within the victim’s AWS account. If the victim’s CDK has permissions to read and write to the compromised bucket, the attacker could inject malicious CloudFormation templates. This could result in the creation of privileged resources or backdoors in the victim’s account, effectively granting the attacker administrative privileges. Aqua’s findings revealed that approximately 1% of CDK users were vulnerable to this attack vector, highlighting the urgent need for enhanced security practices among AWS users.
In response to the vulnerability, AWS has implemented measures to ensure that assets are only uploaded to buckets owned by the user’s account. Customers are encouraged to customize their bucket names during the bootstrapping process to avoid predictability. Additionally, AWS has reached out to potentially affected users to inform them about necessary updates and security checks. As cloud security continues to evolve, this incident underscores the importance of adopting robust security practices, including keeping AWS account IDs confidential and using unique identifiers for S3 buckets to mitigate risks associated with potential account takeovers.
