What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-03-16 · updated 2026-06-17
• Weakness: CWE-283

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. This issue only affects users of the Bedrock AgentCore Starter Toolkit before version v0.1.13 who build or have built 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. To remediate this issue, customers should upgrade to version v0.1.13.

Affected products

• AWS Bedrock AgentCore Starter Toolkit: before 0.1.13 — fixed in 0.1.13

How to fix

Upgrade to a fixed version: AWS Bedrock AgentCore Starter Toolkit 0.1.13. Check the vendor advisory for mitigations.

References

• https://aws.amazon.com/security/security-bulletins/2026-008-AWS/
• https://github.com/aws/bedrock-agentcore-starter-toolkit/releases/tag/v0.1.13

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