The vulnerability identified as CVE-2026-85788 involves an incomplete list of disallowed inputs in the AWS Labs MySQL MCP Server's read-only enforcement mechanism. Specifically, SQL inline comments can be used to bypass the read-only check, allowing execution of statements that the server intended to block. This issue affects awslabs.mysql-mcp-server versions up to and including 1.0.21. The read-only mode is a best-effort feature and relies on the permissions of the configured MySQL user. The vulnerability does not affect AWS service confidentiality or integrity. AWS provides this server as a client-side, self-managed package, and customers control installation and database credential privileges. AWS manages remediation for this cloud-hosted service, and a patch is available as per the vendor advisory.

The vulnerability allows bypassing the read-only enforcement in the AWS Labs MySQL MCP Server, potentially enabling execution of SQL statements that should be blocked. However, the impact is limited because the read-only mode is a best-effort safeguard and the effective security boundary is the permissions of the configured MySQL user. There is no impact on the confidentiality or integrity of AWS services. The vulnerability is rated medium severity with a CVSS score of 5.5.

A patch is available for this vulnerability. Since this is a client-side, self-managed package, customers should update awslabs.mysql-mcp-server to a version later than 1.0.21 where the issue is fixed. AWS manages remediation for this cloud-hosted service; customers should refer to the official AWS Security Bulletin at https://aws.amazon.com/security/security-bulletins/2026-103-aws/ for the most current remediation guidance.