CVE-2026-4269 - Improper S3 ownership verification in Bedrock AgentCore Starter Toolkit

Bulletin ID: 2026-008-AWS Scope: AWS Content Type: Important (requires attention) Publication Date: 2026/03/16 11:15 AM PDT Description: A missing S3 ownership verification in the Bedrock AgentCore Starter Toolkit before version v0.1.13 may allow a remote actor to inject code during the build process, leading to code execution in the AgentCore Runtime. Impacted versions: All versions of Bedrock AgentCore Starter Toolkit versions before v0.1.13. This issue only affects users of the Bedrock AgentCore Starter Toolkit before version v0.1.13 who build the Toolkit after September 24, 2025. Any users on a version >=v0.1.13, and any users on previous versions who built the toolkit before September 24, 2025 are not affected. Please refer to the article below for the most up-to-date and complete information related to this AWS Security Bulletin.