CVE-2026-83551

The @step and @remote decorator pipeline component of the Amazon SageMaker Python SDK stores the HMAC signing key used for payload integrity verification in cleartext within SageMaker DescribePipeline API responses (CWE-312, cleartext storage of sensitive information). An authenticated remote user with high privileges in the same AWS account can call DescribePipeline, extract the signing key, and forge valid integrity signatures for specially crafted function payloads. Successful abuse lets the attacker achieve code execution in another user's pipeline execution context within the same AWS account. Users of the SageMaker Python SDK before v3.11.0 (v3 line) and before v2.256.0 (v2 line) who use the @step/@remote pipeline feature are affected. No public proof-of-concept is known, the flaw is not in CISA KEV, and EPSS estimates only a 0.4% probability of exploitation within 30 days.

What to do: Upgrade the SageMaker Python SDK to v3.11.0 or later (for the 3.x line) or v2.256.0 or later (for the 2.x line). In the interim, audit IAM policies for which principals in the account can call sagemaker:DescribePipeline, since that API is the key-exposure vector, and review recent pipeline executions in the account for unexpected or unapproved function payloads. Note the flaw requires an already-authenticated, high-privilege user in the same AWS account, so cross-account exposure is not indicated by the data.