CVE-2026-1143 is a buffer overflow vulnerability identified in the TOTOLINK A3700R router firmware version 9.1.2u.5822_B20200513. The vulnerability resides in the setWiFiEasyGuestCfg function of the /cgi-bin/cstecgi.cgi endpoint, which processes the ssid argument. An attacker can remotely send a specially crafted request manipulating the ssid parameter to overflow a buffer, leading to memory corruption. This can enable arbitrary code execution with elevated privileges on the device, potentially allowing full control over the router. The vulnerability requires no authentication or user interaction, making it highly exploitable over the network. The CVSS 4.0 base score is 8.7 (high severity), reflecting the ease of exploitation and the significant impact on confidentiality, integrity, and availability. No patches are currently linked, and while no active exploitation has been reported, a public exploit is available, increasing the urgency for mitigation. Exploitation could lead to network compromise, interception or manipulation of traffic, and disruption of network services. The vulnerability affects a specific firmware version, so devices running other versions may not be vulnerable. The router is commonly used in small to medium business and home environments, which may serve as entry points into larger organizational networks if compromised.

For European organizations, exploitation of CVE-2026-1143 could result in severe consequences including unauthorized access to internal networks, interception and manipulation of sensitive data, and disruption of critical network services. Compromised routers could be used as pivot points for lateral movement within corporate networks, increasing the risk of broader cyberattacks such as ransomware or espionage. The confidentiality of communications passing through the affected routers is at risk, as attackers may intercept or alter traffic. Integrity of network configurations and data can be compromised, potentially leading to persistent backdoors or denial of service conditions. Availability of network connectivity may be disrupted, impacting business operations. Organizations relying on TOTOLINK A3700R devices in their infrastructure, especially those without network segmentation or adequate monitoring, face heightened exposure. The presence of a public exploit increases the likelihood of opportunistic attacks targeting unpatched devices across Europe.

1. Immediately identify all TOTOLINK A3700R devices running firmware version 9.1.2u.5822_B20200513 within the network. 2. Apply vendor-provided patches or firmware updates as soon as they become available; monitor TOTOLINK’s official channels for updates. 3. If patches are not yet available, disable remote management interfaces or restrict access to trusted IP addresses only. 4. Implement network segmentation to isolate vulnerable devices from critical systems and sensitive data. 5. Monitor network traffic for unusual patterns or attempts to access /cgi-bin/cstecgi.cgi endpoints with suspicious ssid parameters. 6. Employ intrusion detection/prevention systems (IDS/IPS) with signatures targeting this exploit once available. 7. Educate IT staff about this vulnerability and the importance of timely patching and access controls. 8. Consider replacing vulnerable devices with more secure alternatives if patching is not feasible. 9. Regularly audit device firmware versions and configurations to prevent future exposure. 10. Maintain an incident response plan to quickly address potential compromises stemming from this vulnerability.