CVE-2025-51663 is a vulnerability identified in the IPRateLimit feature of FileCodeBox, a file sharing and collaboration platform, affecting versions up to 2.2. The vulnerability arises because the application trusts the X-Real-IP and X-Forwarded-For HTTP headers to determine the client's IP address for rate limiting purposes. Attackers can exploit this by spoofing these headers, effectively bypassing IP-based rate limiting and failed attempt restrictions. This allows an attacker to perform denial-of-service (DoS) attacks by overwhelming the service with requests or to brute force share codes without being blocked by the rate limiting mechanism. The vulnerability does not require authentication or user interaction, increasing its exploitability. The CVSS v3.1 base score is 7.5, reflecting a high severity due to network attack vector, low attack complexity, no privileges required, no user interaction, and a significant impact on availability. The weakness corresponds to CWE-305, which involves insufficient validation of input leading to security bypass. No patches or known exploits are currently documented, but the risk remains high given the nature of the flaw. The vulnerability impacts the confidentiality and integrity minimally but severely affects availability by enabling DoS attacks. The reliance on HTTP headers for IP identification is a common misconfiguration in web applications behind proxies or load balancers, making this a critical implementation flaw in FileCodeBox's rate limiting logic.

For European organizations, this vulnerability poses a significant risk to the availability of FileCodeBox services, which may be used for internal and external file sharing and collaboration. Successful exploitation can lead to denial-of-service conditions, disrupting business operations and potentially causing data access delays. Additionally, the ability to brute force share codes could lead to unauthorized access to shared files, risking data leakage or compliance violations under regulations such as GDPR. Organizations relying solely on IP-based rate limiting for security controls will find these protections ineffective, increasing exposure to automated attacks. The disruption could affect sectors with high dependency on secure file sharing, including finance, healthcare, and government agencies. Moreover, the attack can be launched remotely without authentication, increasing the attack surface. The lack of known exploits currently provides a window for proactive mitigation, but the vulnerability's characteristics suggest it could be weaponized quickly once publicly known. The impact on confidentiality and integrity is limited but non-negligible if brute force leads to unauthorized data access. Overall, the threat undermines trust in FileCodeBox's security mechanisms and could lead to operational and reputational damage.

To mitigate CVE-2025-51663, organizations should implement the following specific measures: 1) Avoid relying solely on HTTP headers like X-Real-IP and X-Forwarded-For for client IP identification; instead, configure trusted proxies or load balancers to sanitize and validate these headers or use alternative methods such as direct connection IPs or secure proxy protocols. 2) Implement additional authentication and authorization controls on share codes to reduce the risk of brute force attacks, such as multi-factor authentication or rate limiting based on user accounts rather than IP addresses. 3) Deploy Web Application Firewalls (WAFs) with rules to detect and block suspicious header spoofing or anomalous request patterns. 4) Monitor logs for unusual access patterns, including rapid repeated requests with varying spoofed IP headers. 5) Segment and isolate FileCodeBox services within the network to limit the blast radius of potential DoS attacks. 6) Engage with FileCodeBox vendors or community to obtain patches or updates addressing this vulnerability as they become available. 7) Educate security teams about the risks of trusting client-supplied headers and encourage secure coding practices. These steps go beyond generic advice by focusing on architectural changes and enhanced monitoring tailored to the nature of the vulnerability.