Improper S3 ownership verification in Bedrock AgentCore Starter Toolkit
Date: 2026-03
Affected: pip/bedrock-agentcore-starter-toolkit
Attack vector: rce
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2026-4269
CWE: CWE-283
CWE-340
CVSS: 7.5 (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H)

## Summary An issue has been identified in the Bedrock AgentCore Starter Toolkit versions prior to v0.1.13 that may allow a remote actor to inject code during the build process, leading to code execution in the AgentCore Runtime. ## Impact A remote actor could inject code during the build process, leading to code execution in the AgentCore Runtime and a complete loss of confidentiality, integrity, and availability of the affected AgentCore resource. 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 date are not affected. ## Patches This issue has been addressed in version v0.1.13. AWS recommends upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes. ## Workarounds N/A ## References If you have any questions or comments about this advisory, contact [AWS/Amazon] Security via our [vulnerability reporting page](https://aws.amazon.com/security/vulnerability-reporting) or directly via email to [aws-security@amazon.com](mailto:aws-security@amazon.com). Please do not create a public GitHub issue.


Mitigations:

Architectural layers (MAESTRO):