CVE-2026-125271: AWS API MCP Server Security Policy Bypass via Incorrect Operation Name Normalization

Published Nov 10, 2026

Updated

Incorrect normalization of operation names in the custom security policy enforcement in awslabs aws-api-mcp-server before 1.5.1 might allow an actor to execute AWS API operations across AWS services that the operator's security policy was configured to deny or require elicitation for, via calls to operations whose names contain consecutive capital letters.

To remediate this issue, users should upgrade to version 1.5.1.

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 1.5.1

Event History

Nov 10, 2026

CVE Published

via MITRE·04:33 PM

Data Sourced

via MITRE·04:33 PM

DescriptionSeverityWeakness

Frequently Asked Questions

Which deployments are affected?

Deployments using awslabs aws-api-mcp-server before version 1.5.1 are affected if they rely on its custom security policy enforcement for denied operations or operations requiring elicitation.

What does an attacker need to exploit this issue?

An attacker needs to invoke an AWS API operation through the server whose operation name contains consecutive capital letters. The issue can allow such calls to bypass policy rules that were intended to deny the operation or require elicitation.

Is user interaction required?

The supplied CVSS vector indicates user interaction is required (UI:R), while no privileges are required (PR:N).

What should be done if the server cannot be upgraded immediately?

The provided information identifies upgrading to version 1.5.1 as the remediation. It does not provide a documented temporary mitigation.

CVE-2026-125271: AWS API MCP Server Security Policy Bypass via Incorrect Operation Name Normalization

Remediation

Event History

Frequently Asked Questions

Which deployments are affected?

What does an attacker need to exploit this issue?

Is user interaction required?

What should be done if the server cannot be upgraded immediately?

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Resources

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Frequently Asked Questions

Which deployments are affected?

What does an attacker need to exploit this issue?

Is user interaction required?

What should be done if the server cannot be upgraded immediately?