aws-cdk-lib: OS Command Injection in NodejsFunction Bundling

Summary

AWS CDK (aws-cdk-lib) is an open-source framework for defining cloud infrastructure in code and provisioning it through AWS CloudFormation. OS command injection in the NodejsFunction local bundling pipeline in aws-cdk-lib before 2.245.0 (2.246.0 on Windows) might allow a threat actor who controls the value of one or more bundling properties (externalModules, define, loader, inject, or esbuildArgs) to execute arbitrary commands on the host running the CDK toolchain via injected shell metacharacters. This issue requires the threat actor to control the value of one or more of the affected bundling properties in the CDK application.

Impact

During local Lambda bundling, NodejsFunction assembled an esbuild command string from the bundling properties externalModules, define, loader, inject, and esbuildArgs and executed it via a shell (bash -c on Linux/macOS, cmd /c on Windows) through spawnSync. The property values were interpolated without escaping or validation, so values containing shell metacharacters could execute arbitrary commands with the privileges of the user running cdk synth, cdk deploy, or cdk diff. Exploitation requires a threat actor to control one or more of the affected property values in the CDK application — for example via an untrusted npm dependency that vends a wrapper construct, or via a pull request that introduces untrusted values.

Impacted versions:

< 2.245.0 (on Windows, < 2.246.0)

Patches

This issue has been addressed in aws-cdk-lib version 2.245.0 (PR #37292), with a Windows-specific regression fix in 2.246.0 (PR #37412). The fix replaces shell-based command execution with array-based spawnSync invocation that does not invoke a shell. We recommend upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes.

Workarounds

Ensure the values supplied to NodejsFunction bundling properties (externalModules, define, loader, inject, esbuildArgs) originate only from trusted sources, and audit third-party constructs and pull requests that set them. Upgrading to a fixed version is the recommended remediation.

References

If you have any questions or comments about this advisory, we ask that you contact AWS Security via our vulnerability reporting page or directly via email to aws-security@amazon.com. Please do not create a public GitHub issue.

Acknowledgement

AWS would like to thank the external researcher Hesham Ashraf who reported this issue through the AWS Vulnerability Disclosure Program (HackerOne) for collaborating on it through the coordinated vulnerability disclosure process.