CVE-2026-30618 in Fay
Summary
by MITRE • 07/16/2026
xszyou Fay 4.3.1 contains a remote code execution vulnerability in its MCP STDIO server management and command execution handling. A remote attacker can access the publicly exposed MCP management interface and configure an MCP STDIO server with attacker-controlled commands and parameters, resulting in execution of arbitrary commands on the server. Successful exploitation allows arbitrary command execution within the context of the Fay service.
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Analysis
by VulDB Data Team • 07/16/2026
The vulnerability in xszyou Fay 4.3.1 represents a critical remote code execution flaw that stems from inadequate input validation and privilege separation within the MCP STDIO server management component. This issue affects the system's command execution handling mechanism, where the application fails to properly sanitize user-supplied parameters when configuring management interfaces. The vulnerability exists because the MCP management interface lacks proper authentication checks and authorization controls, allowing any remote attacker to establish connections and manipulate system commands through publicly exposed endpoints.
The technical implementation flaw resides in how the application processes STDIO server configurations, where attacker-controlled inputs are directly incorporated into command execution contexts without adequate sanitization or parameter validation. This design weakness creates a path for arbitrary code injection where malicious users can inject commands that execute within the privileges of the Fay service account. The vulnerability is classified as a command injection issue under CWE-77 and aligns with ATT&CK technique T1059.001 for command and script injection, specifically targeting remote execution capabilities.
Operational impact assessment reveals that successful exploitation provides attackers with complete control over the affected server, enabling them to execute arbitrary commands with the privileges of the Fay service user. This level of access typically translates to full system compromise, allowing threat actors to install backdoors, exfiltrate data, or establish persistent access through lateral movement. The vulnerability's exposure through publicly accessible interfaces significantly amplifies its risk profile, as it requires no special network positioning or local access to exploit.
Mitigation strategies should focus on implementing comprehensive input validation and parameter sanitization within the MCP management components, enforcing strict authentication and authorization controls on all administrative interfaces, and restricting public exposure of management endpoints through firewall rules or network segmentation. Organizations should deploy web application firewalls to detect and block suspicious command injection attempts, while also implementing principle of least privilege configurations for service accounts. Regular security updates and patch management procedures should be enforced to address similar vulnerabilities in related components. The remediation approach aligns with ATT&CK mitigation techniques focusing on input validation and access control hardening, ensuring that command execution contexts are properly isolated from user-supplied inputs.