CVE-2026-1155 identifies a critical buffer overflow vulnerability in the Totolink LR350 wireless router firmware version 9.3.5u.6369_B20220309. The vulnerability resides in the setWiFiEasyGuestCfg function, which processes the ssid parameter via the /cgi-bin/cstecgi.cgi endpoint. Due to insufficient bounds checking on the ssid argument, an attacker can supply a specially crafted input that overflows the buffer, potentially overwriting adjacent memory. This flaw can be exploited remotely without authentication or user interaction, as the vulnerable CGI script is accessible over the network. The buffer overflow can lead to arbitrary code execution with elevated privileges, allowing attackers to take full control of the device. This compromises the router’s confidentiality, integrity, and availability, enabling activities such as network traffic interception, device manipulation, or denial of service. The CVSS 4.0 score of 8.7 reflects the high impact and ease of exploitation. Although no active exploitation in the wild has been reported, a public exploit is available, increasing the urgency for remediation. The vulnerability affects a specific firmware version, so organizations must verify their device versions to assess exposure. The lack of authentication requirement and remote attack vector significantly raise the threat level, especially for routers with exposed management interfaces or those deployed in sensitive environments.

For European organizations, exploitation of CVE-2026-1155 could result in severe security breaches. Compromised routers can serve as entry points for lateral movement within corporate networks, leading to data exfiltration, espionage, or disruption of business operations. The integrity of network traffic could be undermined, affecting confidentiality of sensitive communications. Availability risks include potential denial of service or device bricking, impacting business continuity. Organizations relying on Totolink LR350 routers in critical infrastructure, small and medium enterprises, or public sector networks may face heightened risks. The vulnerability’s remote exploitability without authentication increases the likelihood of attacks, especially in environments where routers are internet-facing or poorly segmented. Additionally, attackers could leverage compromised devices to launch broader attacks such as botnets or ransomware campaigns. Given the public availability of exploits, the threat landscape is poised to escalate rapidly without timely mitigation.

European organizations should immediately verify if their networks use Totolink LR350 routers running firmware version 9.3.5u.6369_B20220309. If so, they should seek firmware updates or patches from Totolink; if no official patch is available, consider temporary mitigations such as disabling remote management interfaces and restricting access to the /cgi-bin/cstecgi.cgi endpoint via firewall rules or network segmentation. Network administrators should monitor router logs for suspicious requests targeting the setWiFiEasyGuestCfg function or unusual ssid parameter values. Employ intrusion detection/prevention systems (IDS/IPS) with signatures for this vulnerability to detect and block exploit attempts. Implement strict network access controls to limit exposure of management interfaces to trusted internal networks only. Regularly audit and update router firmware to the latest secure versions. Additionally, consider replacing affected devices if patches are unavailable or delayed, especially in high-risk environments. User education on the risks of exposed network devices and maintaining strong network segmentation can further reduce impact.