CVE-2025-7913 is a critical buffer overflow vulnerability identified in the TOTOLINK T6 router, specifically version 4.1.5cu.748_B20211015. The flaw exists in the MQTT Service component, within the updateWifiInfo function. The vulnerability arises when the serverIp argument is manipulated, leading to a buffer overflow condition. This type of vulnerability can allow an attacker to overwrite memory, potentially enabling arbitrary code execution or causing a denial of service. The attack can be launched remotely without requiring user interaction or prior authentication, increasing its risk profile. The CVSS 4.0 score of 8.7 (high severity) reflects the ease of exploitation (network attack vector, low complexity) and the significant impact on confidentiality, integrity, and availability (all rated high). Although no known exploits are currently reported in the wild, the public disclosure of the exploit code increases the likelihood of exploitation attempts. The vulnerability affects a widely deployed consumer and small office router model, which is often used to provide internet connectivity and local network management. The MQTT Service is typically used for lightweight messaging, and its compromise could allow attackers to manipulate network configurations or intercept sensitive data. The absence of an official patch link suggests that remediation may not yet be available, emphasizing the need for immediate mitigation actions.

For European organizations, this vulnerability poses a significant risk, especially for small and medium enterprises (SMEs) and home office environments that rely on TOTOLINK T6 routers for network connectivity. Successful exploitation could lead to unauthorized access to internal networks, interception or manipulation of network traffic, and potential lateral movement within corporate environments. This could result in data breaches, disruption of business operations, and compromise of sensitive information. Given the remote exploitability without authentication, attackers could target vulnerable devices en masse, potentially leading to widespread denial of service or botnet recruitment. The impact is heightened in sectors with critical infrastructure or sensitive data, such as finance, healthcare, and government agencies, where network integrity and confidentiality are paramount. Additionally, the vulnerability could be leveraged as an entry point for more sophisticated attacks, including ransomware deployment or espionage campaigns targeting European entities.

Immediate mitigation steps include isolating affected TOTOLINK T6 devices from critical network segments and the internet where possible. Network administrators should monitor network traffic for unusual MQTT activity or unexpected connections to the updateWifiInfo function. Implementing network-level filtering to block unauthorized MQTT traffic can reduce exposure. Organizations should contact TOTOLINK support for official patches or firmware updates and apply them promptly once available. In the interim, consider replacing vulnerable devices with models from vendors with active security support. Employ network segmentation to limit the impact of a compromised device and enforce strict access controls on management interfaces. Regularly audit router configurations and logs for signs of compromise. Additionally, educating users about the risks and encouraging secure network practices can help reduce the attack surface. Deploying intrusion detection/prevention systems (IDS/IPS) tuned to detect buffer overflow attempts targeting MQTT services can provide early warning and automated response capabilities.