CVE-2025-6137 is a critical buffer overflow vulnerability identified in the TOTOLINK T10 router firmware version 4.1.8cu.5207. The flaw exists in the HTTP POST request handler component, specifically within the setWiFiScheduleCfg function of the /cgi-bin/cstecgi.cgi file. This function processes the 'desc' argument, which, when manipulated with crafted input, triggers a buffer overflow condition. Because the vulnerability is exploitable remotely without requiring user interaction or prior authentication, an attacker can send specially crafted HTTP POST requests to the affected device to execute arbitrary code or cause a denial of service. The vulnerability has a CVSS 4.0 base score of 8.7 (high severity), with attack vector network (AV:N), low attack complexity (AC:L), no privileges required (PR:L - low privileges), no user interaction (UI:N), and high impact on confidentiality, integrity, and availability (VC:H, VI:H, VA:H). Although no public exploits are currently known in the wild, the exploit code has been disclosed publicly, increasing the risk of exploitation. The vulnerability affects a widely deployed consumer and small office/home office (SOHO) router model, which is often used to provide Wi-Fi connectivity and network routing. Successful exploitation could allow attackers to gain control over the router, intercept or manipulate network traffic, disrupt network availability, or pivot to internal networks, posing significant security risks.

For European organizations, especially small and medium enterprises (SMEs) and residential users relying on TOTOLINK T10 routers, this vulnerability poses a substantial threat. Compromise of these routers could lead to unauthorized access to internal networks, interception of sensitive data, and disruption of business operations due to network outages. Given the router's role as a network gateway, attackers could launch further attacks against connected devices, including data exfiltration or lateral movement within corporate networks. Critical infrastructure or organizations with remote offices using these devices may face increased risk of espionage or sabotage. The high impact on confidentiality, integrity, and availability means that sensitive communications could be exposed or altered, and network services could be rendered unavailable. The remote and unauthenticated nature of the exploit increases the likelihood of widespread attacks if threat actors target vulnerable devices in Europe.

1. Immediate firmware upgrade: TOTOLINK should be contacted to obtain and deploy a patched firmware version addressing CVE-2025-6137. If no patch is available, users should consider replacing the device with a secure alternative. 2. Network segmentation: Isolate vulnerable TOTOLINK T10 devices from critical internal networks to limit potential lateral movement in case of compromise. 3. Restrict remote management: Disable or restrict remote HTTP access to the router’s management interface, ideally limiting access to trusted IP addresses or VPN connections only. 4. Monitor network traffic: Implement intrusion detection systems (IDS) or network monitoring tools to detect anomalous HTTP POST requests targeting /cgi-bin/cstecgi.cgi or unusual traffic patterns indicative of exploitation attempts. 5. Use strong authentication and change default credentials: Although exploitation does not require authentication, ensuring strong passwords reduces risk from other attack vectors. 6. Educate users and administrators about the vulnerability and signs of compromise to enable rapid detection and response. 7. Implement network-level protections such as web application firewalls (WAFs) or filtering rules to block suspicious payloads targeting the vulnerable endpoint.