The vulnerability is a missing token audience validation in the OAuth authentication path of AWS API MCP Server. An attacker who can obtain an access token issued to a different application by the same identity provider can present that token to the server without rejection. This allows a local user to execute AWS operations with the server’s configured permissions, effectively gaining privileged access to AWS resources that the server is authorized to manipulate.

Amazon Web Services, product AWS API MCP Server, versions prior to 1.6.0 on any supported platform, regardless of operating system or deployment method.

The CVSS score of 7.3 classifies the issue as high severity, indicating significant risk if exploited. The EPSS score is not available, so precise exploit probability cannot be quantified, but the absence of a Public KEV listing suggests no known public exploitation yet. The likely attack vector is local or internal: a user who can obtain a valid OAuth token from the same identity provider can craft a request to the server and bypass audience checks to perform arbitrary AWS calls using privileged credentials.