CVE-2025-6514 is a critical security vulnerability classified under CWE-78 (Improper Neutralization of Special Elements used in an OS Command, commonly known as OS command injection). The vulnerability affects mcp-remote version 0.0.5, a client tool that connects to MCP servers. The flaw occurs when mcp-remote processes the authorization_endpoint response URL received from MCP servers without properly sanitizing or validating the input. An attacker controlling or able to influence an untrusted MCP server can craft a malicious authorization_endpoint URL containing OS command injection payloads. When mcp-remote parses and uses this URL, the injected commands are executed on the client system with the privileges of the mcp-remote process. This can lead to full system compromise, including unauthorized disclosure, modification, or destruction of data, and disruption of service. The CVSS 3.1 base score of 9.6 reflects the vulnerability's critical nature: it is remotely exploitable over the network (AV:N), requires no privileges (PR:N), but does require user interaction (UI:R). The scope is changed (S:C), meaning exploitation affects resources beyond the vulnerable component. Confidentiality, integrity, and availability impacts are all rated high (C:H/I:H/A:H). Although no known exploits are reported in the wild yet, the severity and ease of exploitation make this a high-priority issue. The lack of available patches at the time of publication increases the urgency for mitigations and monitoring. The vulnerability highlights the importance of input validation and secure handling of external data in client-server interactions, especially when dealing with authorization endpoints that may be influenced by untrusted entities.

For European organizations, the impact of CVE-2025-6514 could be severe. Organizations using mcp-remote 0.0.5 to connect to MCP servers risk remote code execution attacks that can lead to full system compromise. This threatens confidentiality by exposing sensitive data, integrity by allowing unauthorized modifications, and availability by enabling denial-of-service conditions. Critical infrastructure, financial institutions, and technology companies relying on MCP infrastructure could face operational disruptions and data breaches. The vulnerability’s exploitation could facilitate lateral movement within networks, enabling attackers to escalate privileges and access other critical systems. Given the high CVSS score and the scope of affected systems, the potential for widespread damage is significant, especially if attackers leverage this vulnerability in targeted campaigns. The requirement for user interaction means phishing or social engineering could be vectors to trigger exploitation, increasing risk in environments with less security awareness. The absence of patches means organizations must rely on mitigations and monitoring until updates are available, increasing exposure time. Regulatory compliance risks also arise, as breaches involving this vulnerability could lead to violations of GDPR and other data protection laws, resulting in fines and reputational damage.

To mitigate CVE-2025-6514, European organizations should immediately implement the following measures: 1) Avoid connecting mcp-remote 0.0.5 clients to untrusted or unknown MCP servers to reduce exposure to malicious authorization_endpoint URLs. 2) Employ network segmentation and firewall rules to restrict mcp-remote’s network access only to trusted MCP servers. 3) Implement strict input validation and sanitization for all data received from MCP servers, especially the authorization_endpoint URL, to prevent command injection payloads from being executed. 4) Run mcp-remote with the least privileges possible, ideally within a sandboxed or containerized environment, to limit the impact of any successful exploitation. 5) Monitor logs and network traffic for unusual activity related to mcp-remote connections and command execution attempts. 6) Educate users about the risks of interacting with untrusted MCP servers and the importance of verifying server authenticity. 7) Stay alert for official patches or updates from the mcp-remote maintainers and apply them promptly once available. 8) Consider deploying host-based intrusion detection systems (HIDS) to detect anomalous command executions. 9) Review and update incident response plans to include scenarios involving OS command injection attacks. These targeted actions go beyond generic advice by focusing on controlling the attack surface, hardening the client environment, and enhancing detection capabilities.