CVE-2026-125271 · AI agents & MCP
NO FIX YET · SEE WHAT TO DO
AWS API MCP Server normalizes operation names incorrectly, so names with consecutive capital letters never match a correctly written denyList or elicitList entry. An attacker can run AWS API operations the operator's security policy was meant to block or require confirmation for.
first public Nov 10, 2026 · 2 sources
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Teams that run AWS API MCP Server versions from 0.2.13 up to but not including 1.5.1 and rely on its denyList or elicitList policy to restrict AWS operations. Forks or derivative code carry the same flaw until they are patched. Servers on 1.5.1 or later, or servers without a custom security policy, are not affected by this bypass.
Not affected if no-custom-security-policy, version-1.5.1-or-later
Who cares aws, aws-api-mcp-server, lab-disclosure, mcp, self-hosted
>= 0.2.13 and < 1.5.1.1.5.1, and patch any forked or derivative code.CVE-2026-125271 - AWS API MCP Server Security Policy Bypass via Incorrect Operation Name Normalization
Bulletin ID: 2026-176-AWS Scope: AWS Content Type: Important (requires attention) Publication Date: 11/10/2026 08:30 AM PST
Description:
AWS API MCP Server is an open source Model Context Protocol (MCP) server that customers run to let AI assistants manage their AWS accounts through AWS API calls.
We identified CVE-2026-125271, an issue in the custom security policy enforcement of AWS API MCP Server versions between 0.2.13 and 1.5.0. The server normalized operation names incorrectly before comparing them to the operator's security policy, so operations whose names contain consecutive capital letters never matched a correctly written denyList or elicitList entry. This might allow an actor to execute AWS API operations that the operator's security policy was configured to deny or require elicitation for.
Impacted versions: >= 0.2.13 AND < 1.5.1
Resolution:
This issue has been addressed in awslabs.aws-api-mcp-server version 1.5.1. We recommend upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes.
Workarounds:
There is no workaround other than upgrading.
References:
Acknowledgement:
We would like to thank Syed Anas Mohiuddin for collaborating on this issue through the coordinated vulnerability disclosure process.
Please email aws-security@amazon.com with any s ecurity questions or concerns.
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