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.