CVE-2026-8596: CVE-2026-8596: Remote Code Execution via Cleartext HMAC Key in Amazon SageMaker Python SDK

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CVE-2026-8596: Remote Code Execution via Cleartext HMAC Key in Amazon SageMaker Python SDK

Vulnerability ID: CVE-2026-8596
CVSS Score: 7.2
Published: 2026-05-21

The Amazon SageMaker Python SDK is vulnerable to arbitrary code execution due to the cleartext storage of a symmetric HMAC signing key in job environment variables. An authenticated attacker with Describe permissions can extract this key to forge valid integrity signatures for malicious model artifacts.

TL;DR

SageMaker Python SDK leaked symmetric HMAC keys in job environment variables, allowing attackers to forge signatures and achieve RCE via malicious model artifacts.

⚠️ Exploit Status: POC

Technical Details

CWE ID: CWE-312
Attack Vector: Network
CVSS Score: 7.2 (High)
EPSS Score: 0.10%
Impact: Arbitrary Code Execution
Exploit Status: Proof of Concept
KEV Status: Not Listed

Affected Systems

Amazon SageMaker Python SDK ModelBuilder component
Amazon SageMaker Python SDK Serve component
AWS SageMaker Inference Containers
Amazon SageMaker Python SDK (v2): >= 2.199.0, < 2.257.2 (Fixed in: 2.257.2)
Amazon SageMaker Python SDK (v3): >= 3.0.0, < 3.8.0 (Fixed in: 3.8.0)

Mitigation Strategies

Upgrade SageMaker Python SDK to patched versions
Rebuild existing models using the updated SDK
Restrict IAM roles for SageMaker API and S3 access

Remediation Steps:

Update the Amazon SageMaker Python SDK to version 2.257.2 or 3.8.0.
Identify all models and remote functions created with vulnerable SDK versions.
Rebuild and redeploy identified artifacts to generate new ECDSA signatures.
Audit IAM policies to enforce least privilege on sagemaker:DescribeTrainingJob and s3:PutObject.

References

Read the full report for CVE-2026-8596 on our website for more details including interactive diagrams and full exploit analysis.

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