aws-mcp-server unauthenticated RCE (CVE-2026-5058)

Overview

A critical command injection vulnerability, tracked as CVE-2026-5058, has been identified in the aws-mcp-server. This flaw allows a remote attacker to execute arbitrary operating system commands on an affected server without requiring any authentication. The vulnerability stems from improper input validation when processing the allowed commands list, enabling an attacker to inject and execute malicious code with the privileges of the server process.

Technical Details

The specific flaw exists within the server’s handling of user-supplied input for command execution. The system fails to properly sanitize a string before passing it to a system call. An attacker can craft a network request containing malicious commands, which the server will then execute. This issue was reported as ZDI-CAN-27968. The CVSS v3.1 base score is 9.8 (Critical), reflecting the low attack complexity and the lack of required privileges or user interaction.

Impact

Successful exploitation of this vulnerability results in full remote code execution (RCE) in the context of the MCP server. An attacker could leverage this to install malware, exfiltrate data, create a persistent backdoor, or move laterally within a network. Given that the aws-mcp-server is designed to interface with AWS services, a compromise could potentially lead to further cloud resource manipulation or credential theft.

Remediation and Mitigation

The primary remediation is to apply the official security patch provided by the vendor as soon as it is available. System administrators should monitor the vendor’s security advisories for update information.

Until a patch can be applied, consider the following immediate mitigation steps:

• Network Segmentation: Restrict network access to the aws-mcp-server to only trusted IP addresses and necessary networks. Implement strict firewall rules.
• Principle of Least Privilege: Ensure the server process is running with the minimum system privileges required for its function to limit the impact of a potential exploit.
• Monitoring: Review logs for unusual outbound connections or unexpected process execution originating from the server host.

## Security Insight

This vulnerability highlights the persistent risk of command injection in service interfaces, a class of flaw often stemming from the unsafe concatenation of user input with system commands. It echoes the risks seen in other AI/ML tooling, such as recent flaws in LangChain and LangGraph, where overly permissive agent capabilities can lead to system compromise. The critical nature of CVE-2026-5058 underscores the importance of rigorous input validation and sandboxing in any server that interprets and executes commands, especially those connected to cloud management planes.

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