CVE-2026-1158 is a remote buffer overflow vulnerability identified in the Totolink LR350 router firmware version 9.3.5u.6369_B20220309. The vulnerability resides in the setWizardCfg function of the /cgi-bin/cstecgi.cgi component, which handles POST requests. Specifically, the ssid parameter is improperly validated, allowing an attacker to send a crafted POST request that overflows the buffer. This overflow can corrupt memory, potentially enabling arbitrary code execution with elevated privileges on the device. The attack vector is network-based, requiring no authentication or user interaction, making it highly accessible to remote attackers. The vulnerability has a CVSS 4.0 base score of 8.7, reflecting its critical impact on confidentiality, integrity, and availability. Although no confirmed exploits are reported in the wild, a public proof-of-concept exploit exists, increasing the likelihood of exploitation attempts. The flaw can lead to full device compromise, enabling attackers to control network traffic, intercept data, or launch further attacks within the network. The absence of vendor patches at the time of disclosure necessitates immediate mitigation through network segmentation, access restrictions, and monitoring. This vulnerability highlights the importance of secure input validation in embedded device firmware, especially in network infrastructure components.

For European organizations, exploitation of CVE-2026-1158 could result in severe consequences including unauthorized control over affected routers, leading to interception or manipulation of network traffic, disruption of internet connectivity, and potential lateral movement within corporate networks. Compromised devices could serve as footholds for attackers to deploy malware, exfiltrate sensitive data, or launch attacks against other internal systems. Critical infrastructure sectors relying on Totolink LR350 devices for connectivity may experience operational disruptions. The remote, unauthenticated nature of the exploit increases the risk of widespread attacks, especially in environments where these routers are exposed to untrusted networks or the internet. The public availability of an exploit further elevates the threat, as less skilled attackers can leverage it. Overall, the vulnerability poses a significant risk to confidentiality, integrity, and availability of network services in European enterprises and public sector organizations.

1. Immediately restrict access to the management interface of Totolink LR350 devices by implementing firewall rules or network segmentation to limit POST requests to trusted sources only. 2. Monitor network traffic for unusual POST requests targeting /cgi-bin/cstecgi.cgi, especially those containing suspicious ssid parameters. 3. Disable remote management features if not required, or restrict them to secure VPN connections. 4. Apply vendor firmware updates or patches as soon as they become available to address the buffer overflow vulnerability. 5. Conduct regular vulnerability scans and penetration tests focused on network infrastructure devices to detect similar flaws. 6. Implement intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics capable of identifying exploitation attempts against this vulnerability. 7. Educate network administrators about the risks and signs of exploitation related to this vulnerability to enable rapid incident response. 8. Maintain an inventory of all Totolink LR350 devices in use to ensure comprehensive coverage of mitigation efforts.