CVE-2026-5059: aws-mcp-server Command Injection RCE

Overview

A critical command injection vulnerability, tracked as CVE-2026-5059, has been identified in the aws-mcp-server. This flaw, with a maximum CVSS score of 9.8, allows remote, unauthenticated attackers to execute arbitrary code on affected systems. The vulnerability stems from improper input validation when processing the allowed commands list, enabling an attacker to craft malicious strings that are executed as system calls.

Technical Details

The vulnerability, internally identified as ZDI-CAN-27969, exists within the server’s command-handling logic. The aws-mcp-server fails to properly sanitize user-supplied input before passing it to a system call for execution. Because no authentication is required to interact with the vulnerable component, an attacker can send a specially crafted network request to the server. This request bypasses the intended command restrictions, allowing the execution of arbitrary operating system commands with the privileges of the MCP server process.

Impact

Successful exploitation grants an attacker the ability to run any command on the host system. This can lead to a complete compromise of the server, including data theft, installation of persistent malware, or use of the server as a pivot point to attack other internal network resources. Given the high privileges often associated with AWS-related services, the potential impact is severe.

Remediation and Mitigation

The primary remediation is to apply the official security patch provided by the vendor for aws-mcp-server immediately. System administrators should:

1. Patch Immediately: Update the aws-mcp-server to the latest patched version as soon as it is released by the vendor.
2. Restrict Network Access: If patching is delayed, restrict network access to the MCP server’s port (typically 8080 or 8081) using firewall rules. Only allow connections from explicitly trusted, necessary sources.
3. Monitor for Exploitation: Review server logs for unusual command execution attempts or unexpected outbound connections from the server process.

Until a patch is applied, consider the service to be at high risk of compromise from any network-accessible source.

Security Insight

This vulnerability highlights the persistent risk of command injection in tools that bridge high-level APIs with system-level operations, a pattern also seen in recent AI framework flaws like those in LangChain and LangGraph. It underscores the critical need for rigorous input validation and sandboxing in any service that dynamically constructs system commands, especially those designed to interact with privileged cloud environments. The absence of required authentication for such a powerful function represents a significant architectural security oversight.

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