🟠 High | Source: AWS Security Bulletins
A security flaw in the AWS API MCP Server (versions 0.2.13 to 1.3.47) means that if the server fails to load its security policy on startup, it silently continues running without enforcing that policy for the remainder of the process lifetime. This creates a window where an attacker could trigger AWS API operations that the policy was intended to block or gate, bypassing controls the operator believed were in place. Crucially, IAM permissions are unaffected, but any additional guardrails provided by the MCP security policy are rendered ineffective.
Security Architect’s Take: Update the AWS API MCP Server to version 1.3.47 or later immediately, and in the interim enable fail-closed mode on any configured security policies to ensure a startup failure halts the process rather than silently degrading enforcement. Audit your deployment logs for past startup errors that may indicate the policy was previously unenforced.
Original advisory: CVE-2026-16584 - AWS API MCP Server Security Policy Bypass via Startup Failure