CVE-2025-45843 is a high-severity vulnerability identified in the TOTOLINK NR1800X router firmware version V9.1.0u.6681_B20230703. The flaw is an authenticated stack overflow occurring in the setWiFiGuestCfg function, specifically via the ssid parameter. This means that an attacker with valid credentials to the device's management interface can exploit this vulnerability by sending a specially crafted request that manipulates the ssid parameter, causing a stack overflow. Stack overflow vulnerabilities (classified under CWE-121) can lead to arbitrary code execution, allowing an attacker to execute malicious code with the privileges of the affected process. Given the CVSS 3.1 base score of 8.8, the vulnerability is considered high severity, with a vector indicating network attack (AV:N), low attack complexity (AC:L), requiring privileges (PR:L), no user interaction (UI:N), unchanged scope (S:U), and high impact on confidentiality, integrity, and availability (C:H/I:H/A:H). Although exploitation requires authentication, the lack of user interaction and network accessibility increases the risk, especially in environments where default or weak credentials are used or where internal threat actors exist. No known exploits are currently reported in the wild, and no patches have been linked yet, indicating that affected users should prioritize mitigation. The vulnerability affects a specific firmware version of the TOTOLINK NR1800X router, a device commonly used in small to medium business and home environments for wireless networking.

For European organizations, this vulnerability poses a significant risk to network infrastructure security. Exploitation could lead to full compromise of the affected router, allowing attackers to intercept, modify, or disrupt network traffic, potentially leading to data breaches, lateral movement within corporate networks, or denial of service. Given the high impact on confidentiality, integrity, and availability, critical business operations relying on network connectivity could be disrupted. In sectors such as finance, healthcare, and government, where data sensitivity and uptime are paramount, this vulnerability could facilitate espionage, data theft, or sabotage. Additionally, compromised routers could be leveraged as footholds for further attacks or as part of botnets for distributed denial-of-service (DDoS) campaigns. The requirement for authentication somewhat limits exploitation to insiders or attackers who have obtained credentials, but weak credential management practices common in some organizations increase the risk. The absence of patches necessitates immediate risk mitigation to prevent exploitation.

European organizations using TOTOLINK NR1800X routers should take immediate steps to mitigate this vulnerability. First, restrict access to the router management interface by limiting it to trusted internal networks and using strong, unique administrator passwords to prevent unauthorized authentication. Implement network segmentation to isolate management interfaces from general user networks. Monitor router logs for unusual configuration changes or access attempts. Disable guest WiFi features if not required, as the vulnerability is in the guest WiFi configuration function. Until an official patch is released, consider deploying compensating controls such as network-level firewalls or intrusion detection/prevention systems (IDS/IPS) to detect and block suspicious traffic targeting the router's management interface. Regularly check for firmware updates from TOTOLINK and apply patches promptly once available. Conduct security awareness training to reduce the risk of credential compromise. Finally, perform periodic vulnerability assessments and penetration testing focusing on network devices to identify and remediate similar risks proactively.