CVE-2025-66902 identifies a security vulnerability in the Pithikos websocket-server version 0.6.4, specifically within the websocket_server/websocket_server.py file and the WebSocketServer._message_received method. The root cause is an input validation issue where the server does not properly sanitize or validate incoming WebSocket messages. This flaw enables a remote attacker to send crafted messages that can trigger unintended server behavior, including the disclosure of sensitive information or causing the server to behave unexpectedly, potentially leading to denial of service. The vulnerability does not require prior authentication or user interaction, increasing its risk profile. Although no CVSS score or patches are currently available, the vulnerability is publicly disclosed and reserved under CVE-2025-66902. The websocket-server is typically used to facilitate real-time bidirectional communication in web applications, making it a critical component in environments relying on live data streams or interactive services. Exploitation could allow attackers to access sensitive data processed by the server or disrupt service availability, impacting confidentiality and availability. No known exploits have been reported yet, but the lack of patches means systems remain vulnerable. The absence of detailed affected versions beyond 0.6.4 suggests that this version and potentially earlier releases are impacted. The vulnerability highlights the importance of robust input validation in WebSocket implementations to prevent injection or manipulation attacks.

For European organizations, exploitation of this vulnerability could lead to unauthorized access to sensitive information transmitted or processed by the websocket-server, compromising confidentiality. Additionally, attackers could cause unexpected server behavior, including crashes or denial of service, affecting availability of critical real-time applications. Sectors relying heavily on WebSocket communications—such as financial services, telecommunications, and public services—may experience operational disruptions or data breaches. The impact is heightened in environments where the websocket-server is integrated into critical infrastructure or customer-facing platforms. Data privacy regulations like GDPR increase the stakes, as data exposure incidents could result in significant legal and financial penalties. The lack of authentication requirement for exploitation means attackers can target exposed websocket endpoints directly, increasing the attack surface. The vulnerability could also be leveraged as a foothold for further network intrusion or lateral movement if combined with other weaknesses. Overall, the threat poses a significant risk to the confidentiality and availability of services in European organizations using the affected software.

European organizations should immediately audit their environments to identify any deployments of Pithikos websocket-server version 0.6.4 or earlier. Until an official patch is released, implement strict network-level controls to restrict access to websocket-server endpoints, such as IP whitelisting and firewall rules limiting inbound WebSocket connections to trusted sources. Employ Web Application Firewalls (WAFs) with custom rules to detect and block malformed or suspicious WebSocket messages targeting the _message_received handler. Enhance logging and monitoring of WebSocket traffic to identify anomalous patterns indicative of exploitation attempts. Developers should review and harden input validation routines within the WebSocketServer._message_received method, ensuring all incoming data is sanitized and validated against expected formats. Consider deploying WebSocket proxies or gateways that can enforce protocol compliance and filter malicious payloads. Conduct penetration testing focused on WebSocket interfaces to uncover potential exploitation vectors. Finally, maintain close monitoring of vendor advisories for patches or updates addressing this vulnerability and plan for rapid deployment once available.