CVE-2025-5905 is a critical buffer overflow vulnerability identified in the TOTOLINK T10 router, specifically in firmware version 4.1.8cu.5207. The flaw exists in the POST request handler function setWiFiRepeaterCfg within the /cgi-bin/cstecgi.cgi component. An attacker can exploit this vulnerability by manipulating the Password argument in the HTTP POST request to trigger a buffer overflow condition. This vulnerability is remotely exploitable without requiring user interaction or prior authentication, as indicated by the CVSS vector (AV:N/AC:L/AT:N/UI:N/PR:L). The buffer overflow can lead to severe consequences including arbitrary code execution, potentially allowing an attacker to take full control of the affected device. The vulnerability has a high CVSS 4.0 base score of 8.7, reflecting its significant impact on confidentiality, integrity, and availability. Although no public exploit is currently known to be actively used in the wild, the exploit code has been disclosed publicly, increasing the risk of exploitation. The vulnerability affects a widely deployed consumer and small business router model, which is often used to extend WiFi coverage via repeater functionality. Given the nature of the flaw, attackers could leverage it to compromise network infrastructure, intercept or manipulate network traffic, or pivot to other internal systems.

For European organizations, this vulnerability poses a substantial risk, especially for small and medium enterprises (SMEs) and home office environments that rely on TOTOLINK T10 routers for network connectivity and WiFi extension. Successful exploitation could lead to complete compromise of the router, enabling attackers to intercept sensitive communications, deploy malware, or create persistent backdoors within the network. This could result in data breaches, disruption of business operations, and loss of trust. Critical infrastructure or organizations with remote sites using these devices are particularly vulnerable to lateral movement and espionage. The lack of required user interaction and remote exploitability increases the threat level, as attackers can scan for vulnerable devices and launch attacks without alerting users. Additionally, the disclosed exploit code lowers the barrier for attackers, potentially leading to widespread exploitation if patches are not applied promptly.

Organizations should immediately identify all TOTOLINK T10 devices running firmware version 4.1.8cu.5207 within their networks. Since no official patch links are currently provided, it is crucial to monitor TOTOLINK's official channels for firmware updates addressing this vulnerability. In the interim, network administrators should restrict remote management access to these devices by disabling WAN-side access to the router's web interface and limiting management to trusted internal IP addresses only. Implement network segmentation to isolate vulnerable devices from critical systems and sensitive data. Employ intrusion detection and prevention systems (IDS/IPS) to monitor for suspicious POST requests targeting /cgi-bin/cstecgi.cgi. Regularly audit router configurations and logs for signs of exploitation attempts. Consider replacing affected devices with models from vendors with a stronger security track record if patches are delayed. Educate users about the risks of using outdated firmware and the importance of timely updates.