CVE-2025-51663 is a security vulnerability identified in the IPRateLimit feature of FileCodeBox versions up to 2.2. The vulnerability arises because the application relies on HTTP headers X-Real-IP and X-Forwarded-For to determine the client's IP address for enforcing rate limits and restricting failed attempts. Attackers can exploit this by spoofing these headers, effectively bypassing IP-based rate limiting controls. This allows them to perform denial-of-service (DoS) attacks by overwhelming the service with requests or to brute force share codes without triggering the intended protections. The vulnerability does not require authentication or user interaction, making it easier to exploit remotely. The lack of patch information suggests that a fix may not yet be available, increasing the urgency for mitigation. The vulnerability impacts the confidentiality and availability of the service by enabling unauthorized access attempts and potential service disruption. Since FileCodeBox is used for file sharing and collaboration, exploitation could lead to unauthorized data access or service outages. No known exploits have been reported in the wild as of the publication date, but the vulnerability's nature makes it a significant risk. The vulnerability was reserved in June 2025 and published in November 2025, indicating recent discovery and disclosure.

For European organizations, this vulnerability poses a risk primarily to the availability and confidentiality of file sharing services using FileCodeBox. Attackers can bypass rate limiting to launch DoS attacks, potentially disrupting business operations and causing downtime. Additionally, brute forcing share codes could lead to unauthorized access to sensitive files, risking data breaches and compliance violations under regulations like GDPR. Organizations relying on FileCodeBox for internal or external collaboration may face operational disruptions and reputational damage if exploited. The ease of exploitation without authentication increases the threat level, especially for publicly accessible instances. The impact is magnified in sectors with high data sensitivity such as finance, healthcare, and government. Furthermore, the lack of a patch or workaround at the time of disclosure means organizations must rely on defensive controls to mitigate risk. The vulnerability could also be leveraged as part of multi-stage attacks, combining access to sensitive data with further lateral movement or data exfiltration.

To mitigate CVE-2025-51663, organizations should first verify whether they are using FileCodeBox up to version 2.2 and assess exposure to the internet. Immediate steps include configuring the application or reverse proxies to ignore or validate the X-Real-IP and X-Forwarded-For headers, ensuring they cannot be spoofed by untrusted clients. Deploying web application firewalls (WAFs) with rules to detect and block suspicious header manipulation can provide an additional layer of defense. Network-level rate limiting based on source IPs at the firewall or load balancer can help mitigate abuse. Monitoring logs for unusual patterns of failed attempts or excessive requests can aid in early detection. If possible, restrict access to FileCodeBox instances to trusted networks or VPNs to reduce exposure. Organizations should engage with the vendor for patches or updates addressing this vulnerability and apply them promptly once available. Educating users about secure sharing practices and implementing multi-factor authentication for sensitive operations can further reduce risk. Finally, conducting regular security assessments and penetration testing can help identify residual risks related to this vulnerability.