CVE-2026-16584 in aws-api-mcp-server
Summary
by MITRE • 07/23/2026
Improper handling of an initialization failure in AWS API MCP Server from 0.2.13 through 1.3.46 might allow an actor to bypass the user-configured security policy and execute AWS API operations that the policy was set to deny or gate. When initialization of the security policy enforcement data fails at server startup, the policy check is skipped for the lifetime of the process. IAM permissions on the configured credentials remain in effect and are unaffected.
To remediate this issue, users should upgrade to version 1.3.47.
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Analysis
by VulDB Data Team • 07/23/2026
This vulnerability represents a critical security flaw in AWS API MCP Server where improper handling of initialization failures creates a persistent bypass mechanism for security policies. The vulnerability occurs when the server fails to properly initialize its security policy enforcement data structures during startup, resulting in a dangerous state where policy checks are completely disabled for the entire lifetime of the process. This design flaw stems from inadequate error handling and recovery mechanisms that should have been implemented to ensure system integrity during startup phases.
The technical implementation of this vulnerability involves a failure in the server's initialization sequence where specific validation or configuration loading processes may encounter errors, yet the system does not properly terminate or fallback to a secure state. Instead, it continues operating with an incomplete security policy framework, allowing all AWS API operations to proceed without proper authorization checks. This behavior violates fundamental security principles and creates a persistent backdoor that remains active until the process is restarted.
From an operational impact perspective, this vulnerability exposes organizations to significant risk as it allows unauthorized actors to bypass configured security controls that were specifically designed to prevent certain API operations. The affected versions range from 0.2.13 through 1.3.46, indicating a prolonged period where systems could be vulnerable. The vulnerability is particularly concerning because it affects the core authorization mechanism of the MCP server, which is responsible for enforcing user-configured security policies. This creates a scenario where even robust IAM permissions configured at the credential level become irrelevant as the policy enforcement layer itself fails.
The security implications align with CWE-252, which addresses "Unchecked Return Value" and improper error handling in security-critical systems. This vulnerability also maps to ATT&CK technique T1078.004, which covers valid accounts through compromised credentials, as unauthorized access becomes possible through the bypass mechanism rather than traditional credential compromise. The flaw essentially creates a persistent privilege escalation path where an attacker can execute operations that should have been denied by policy configuration.
Organizations affected by this vulnerability should immediately implement mitigation strategies while planning for the mandatory upgrade to version 1.3.47, which contains the necessary fixes to properly handle initialization failures and maintain security policy enforcement even when errors occur during startup. The remediation process requires careful monitoring of system behavior post-upgrade to ensure that the fix has properly resolved the persistent state issue. Additionally, organizations should conduct thorough security assessments to identify any potential exploitation that may have occurred during the vulnerable period, as the bypass could have enabled unauthorized access to AWS resources through API operations that should have been restricted by configured policies.