CVE-2025-67445 is a denial-of-service (DoS) vulnerability identified in the TOTOLINK X5000R router firmware version V9.1.0cu.2415_B20250515. The issue resides in the /cgi-bin/cstecgi.cgi management CGI script, which improperly handles the CONTENT_LENGTH environment variable. Specifically, the CGI uses malloc to allocate memory based on CONTENT_LENGTH + 1 without sufficient bounds checking, leading to potential memory exhaustion or segmentation faults. This vulnerability is exploitable when the lighttpd web server, which hosts the management interface, does not enforce its request size limit. An attacker can craft a large POST request that exceeds expected limits, causing the CGI to allocate excessive memory, resulting in a crash of the management interface. This crash leads to loss of availability of the router's web management interface, effectively causing a denial-of-service condition. The vulnerability is classified under CWE-400 (Uncontrolled Resource Consumption). The attack vector is adjacent network, meaning the attacker must be on the same local network or connected network segment. No authentication or user interaction is required, making exploitation straightforward if network access is available. The CVSS v3.1 base score is 6.5, reflecting medium severity due to the impact on availability without affecting confidentiality or integrity. No patches or mitigations have been officially released at the time of reporting, and no known exploits have been observed in the wild.

The primary impact of CVE-2025-67445 is the loss of availability of the TOTOLINK X5000R router's web management interface. This denial-of-service condition can disrupt administrative access to the device, preventing configuration changes, monitoring, or troubleshooting via the web GUI. For organizations relying on this router model, especially in small to medium business or home office environments, this could lead to prolonged downtime or degraded network management capabilities. Although the vulnerability does not directly compromise confidentiality or integrity, the inability to manage the device could delay incident response or security updates, indirectly increasing risk. Additionally, repeated exploitation could cause device instability or require physical reboot, impacting network reliability. Since the attack requires network adjacency, the threat is more significant in environments where attackers have local network access, such as compromised internal networks or poorly segmented wireless networks. The absence of authentication requirements lowers the barrier to exploitation, increasing the risk in exposed network segments.

To mitigate CVE-2025-67445, organizations should first verify if they are using the affected TOTOLINK X5000R firmware version V9.1.0cu.2415_B20250515. If so, immediate steps include restricting access to the router's management interface by implementing network segmentation and firewall rules to limit access only to trusted administrators and management stations. Enforce strict access controls on the local network to prevent unauthorized users from reaching the device's web interface. Monitor network traffic for unusually large POST requests targeting /cgi-bin/cstecgi.cgi and implement intrusion detection or prevention systems to alert or block such attempts. If possible, disable or restrict the use of the vulnerable CGI endpoint until a patch is available. Contact TOTOLINK support or monitor official channels for firmware updates addressing this vulnerability and apply patches promptly once released. Additionally, consider alternative management methods such as SSH or SNMP if supported and secure. Regularly audit device configurations and logs to detect signs of attempted exploitation. Finally, enforce the request size limits on the lighttpd web server configuration to prevent oversized POST requests from reaching the CGI script.