CVE-2026-112408 - Missing bucket ownership verification in Amazon SageMaker Python SDK default_bucket()
Bulletin ID: 2026-142-AWS
Scope: AWS
Content Type: Important (requires attention)
Publication Date: 10/21/2026 12:30 PM PDT
Description:
The Amazon SageMaker Python SDK is an open-source library for training and deploying machine learning models on Amazon SageMaker. We identified CVE-2026-112408, an issue in the default_bucket() function. The SDK uses a predictably named Amazon S3 bucket and does not check that the caller's AWS account owns it. A remote actor who creates that bucket first could achieve code execution in a remote SageMaker execution environment and obtain IAM credentials.
Impacted versions:
- V2: < 2.257.3
- V3: >= 3.0.0 and < 3.10.0
Resolution:
This issue has been addressed in Amazon SageMaker Python SDK versions 2.257.3 (V2) and 3.10.0 (V3). We recommend upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes.
Workarounds:
If you are not able to upgrade, pass an S3 bucket that your account owns explicitly through the default_bucket parameter of sagemaker.Session (or through the SageMaker SDK configuration file). Do not rely on the auto-generated default bucket name.
References:
Acknowledgement:
We would like to thank Dan Gansel from Upwind Security for collaborating on this issue through the coordinated disclosure process.
Please email aws-security@amazon.com with any security questions or concerns.