CVE-2025-56405 is a security vulnerability identified in the litmusautomation litmus-mcp-server software, specifically in versions up to 0.0.1. The vulnerability allows unauthorized attackers to gain control over the target's MCP (Message Control Protocol) service via the Server-Sent Events (SSE) protocol. SSE is a standard allowing servers to push real-time updates to clients over HTTP. In this context, the vulnerability implies that the MCP service does not properly enforce authentication or authorization checks when handling SSE connections, enabling attackers to manipulate or control the MCP service remotely without valid credentials. This could lead to unauthorized command execution or manipulation of the MCP service's behavior. The absence of a CVSS score and patch information suggests that this vulnerability is newly disclosed and may not yet have an official fix or widespread exploitation. The technical details are limited, but the core issue revolves around insufficient access control in the SSE handling component of the litmus-mcp-server, which is critical for maintaining the integrity and security of communications managed by the MCP service.

For European organizations using litmusautomation's litmus-mcp-server, this vulnerability poses a significant risk. Unauthorized control over the MCP service could allow attackers to disrupt critical messaging or control functions, potentially leading to service outages, data manipulation, or unauthorized data disclosure. Organizations relying on this software for automation, control, or communication tasks could experience operational disruptions, loss of data integrity, and increased risk of lateral movement within their networks. Given the lack of authentication enforcement, attackers could exploit this vulnerability remotely, increasing the attack surface. The impact is particularly severe for sectors where MCP services are integral to industrial control systems, telecommunications, or real-time data processing, which are common in European manufacturing, energy, and telecom industries. The absence of known exploits in the wild currently reduces immediate risk but also highlights the urgency for proactive mitigation before exploitation attempts emerge.

Immediate mitigation should focus on restricting access to the MCP service and its SSE endpoints. Network-level controls such as firewall rules should limit connections to trusted hosts and networks only. Implementing strong authentication and authorization mechanisms around the SSE protocol handling is critical; if the software does not currently support this, organizations should consider deploying reverse proxies or API gateways that enforce these controls. Monitoring and logging SSE connections for unusual activity can help detect attempted exploitation. Since no patches are currently available, organizations should engage with litmusautomation for updates and consider isolating the MCP service in segmented network zones to reduce exposure. Additionally, conducting thorough security assessments of the MCP service configuration and updating to newer versions once patches are released will be essential. Finally, organizations should prepare incident response plans specific to potential MCP service compromises.