This vulnerability (CVE-2026-87913) in AWS Security Agent MCP server prior to version 0.2.0 is due to missing verification of S3 bucket ownership. An attacker can exploit this by using a pre-registered storage bucket whose name is derived from a publicly known AWS account identifier, potentially gaining access to private source archives of scanned workspaces. These archives may contain sensitive information such as credentials and infrastructure state. The vulnerability has a CVSS 3.1 score of 5.9, reflecting medium severity with network attack vector, high complexity, no privileges required, and user interaction needed. AWS has issued an official fix in version 0.2.0 and advises users to verify bucket ownership to prevent unauthorized access.

If exploited, remote attackers could obtain private source archives from scanned workspaces, including sensitive credentials and infrastructure state data. This could lead to unauthorized disclosure of confidential information. The vulnerability does not allow integrity or availability impacts but compromises confidentiality.

An official fix is available in AWS Security Agent MCP server version 0.2.0. Users should upgrade to this version promptly. Additionally, users must verify that the scan output S3 bucket is owned by their own AWS account, as upgrading does not reclaim bucket names that third parties may have already registered. Follow the vendor advisory at https://aws.amazon.com/security/security-bulletins/2026-105-aws/ for detailed remediation guidance.