CVE-2026-18830: Amazon Bedrock AgentCore Input Validation Bypass

CVE-2026-18830 - Issue in Amazon Bedrock AgentCore harness – Insufficient Input Validation Vulnerability Overview Vulnerability ID: CVE-2026-18830 Affected Product: Amazon Bedrock AgentCore harness InvokeHarness API Vulnerability Type: Insufficient Input Validation Release Date: April 8, 2026 Description: This vulnerability allows authenticated users to bypass model invocation and related security controls when executing tool calls. When a recent request contains tool content blocks, the agent event loop can directly invoke named tools without model mediation. Impact Scope Affected Versions: Amazon Bedrock AgentCore harness InvokeHarness API versions prior to July 31, 2026. Potential Impact: Impact is limited to the tools configured on the given harness. A harness with no tools configured cannot execute any tools, while a harness with a restricted set of tools can only execute tools within that set. Remediation Fix: AWS added server-side input validation to the final message of the request to reject caller-provided tool use content blocks before the request reaches the agent event loop. This issue has been fully resolved in AWS managed services. Temporary Workaround: No additional action is required; the mitigation has been automatically applied server-side for all requests. References CVE-2026-18830 Acknowledgements Thanks to Aviyam Ivgi and Hedi Ingber for their report and collaboration in resolving this issue through a coordinated vulnerability disclosure process.

Goal Reached Thanks to every supporter — we hit 100%!

CVE-2026-18830: Amazon Bedrock AgentCore Input Validation Bypass

More from this source