Package vulnerability, severity medium

AWS API MCP Server security policy bypass via operation name normalization (CVE-2026-125271)

Published November 10, 2026

AWS API MCP Server normalized operation names incorrectly before comparing them to the operator's security policy. Operations with consecutive capital letters never matched a correctly written denyList or elicitList entry, which might let an actor run AWS API operations the policy was meant to deny or require elicitation for. Versions 0.2.13 up to but not including 1.5.1 are affected; 1.5.1 fixes it.

What's affected

• awslabs.aws-api-mcp-server (pypi)>=0.2.13 <1.5.1

What to do

1. Upgrade awslabs.aws-api-mcp-server to version 1.5.1 or later.
2. Patch any forked or derivative code to incorporate the fix.
3. There is no workaround other than upgrading.

Check whether you were affected

Pharon tells teams automatically when this affects something they run. To check a machine, run this in Claude Code with the Pharon plugin, in the repository that uses it:

/pharon:check-incident aws-api-mcp-server-policy-bypass-2026-11

References

• https://aws.amazon.com/security/security-bulletins/rss/2026-176-aws/

Notice aws-api-mcp-server-policy-bypass-2026-11, signed with key feed-prod-2026-10 (Ed25519). The Pharon CLI verifies the signature before using a notice.