CVE-2025-45787 is a medium-severity buffer overflow vulnerability affecting the TOTOLINK A3100R router running firmware version V5.9c.1527. The vulnerability arises from improper handling of the 'comment' parameter within the setIpPortFilterRules function. Specifically, the buffer overflow (CWE-121) occurs when the input to the comment parameter exceeds the allocated buffer size, leading to potential memory corruption. This flaw can be exploited remotely over the network without requiring any privileges or user interaction, as indicated by the CVSS vector (AV:N/AC:L/PR:N/UI:N). Successful exploitation could allow an attacker to manipulate the router’s memory, potentially leading to limited confidentiality and integrity impacts such as unauthorized disclosure or modification of data. However, the vulnerability does not directly impact availability. No known exploits are currently reported in the wild, and no patches have been published yet. The vulnerability was reserved in April 2025 and published in May 2025, indicating it is a recent discovery. The router model TOTOLINK A3100R is a consumer-grade device commonly used in home and small office environments, which may limit the scope of impact to those environments. The lack of authentication requirement and remote exploitability make this vulnerability significant for attackers seeking to compromise network devices for lateral movement or data interception.

For European organizations, the impact of this vulnerability depends largely on the deployment of TOTOLINK A3100R routers within their network infrastructure. While TOTOLINK devices are primarily consumer-focused, some small businesses or branch offices may use these routers. Exploitation could allow attackers to gain unauthorized access to network configurations or intercept traffic, potentially leading to data leakage or network manipulation. This is particularly concerning for organizations handling sensitive personal data under GDPR, as any compromise could lead to regulatory penalties. Additionally, compromised routers could be used as footholds for further attacks within corporate networks or as part of botnets for broader malicious campaigns. The medium severity rating reflects limited confidentiality and integrity impact without availability disruption, but the ease of remote exploitation without authentication increases the risk profile. European organizations with remote or distributed offices using these devices should be vigilant, as attackers could exploit this vulnerability to bypass perimeter defenses.

Given the absence of an official patch, European organizations should implement several practical mitigations: 1) Immediately identify and inventory all TOTOLINK A3100R routers in their environment, especially those running firmware V5.9c.1527. 2) Restrict remote management access to these devices by disabling WAN-side administration and limiting access to trusted internal IP ranges. 3) Employ network segmentation to isolate vulnerable routers from critical internal systems, minimizing lateral movement risks. 4) Monitor network traffic for unusual activity or attempts to exploit the setIpPortFilterRules function, using IDS/IPS signatures if available or custom rules targeting suspicious parameter usage. 5) Encourage users and administrators to upgrade to newer firmware versions once patches are released by TOTOLINK or consider replacing affected devices with more secure alternatives. 6) Apply strict firewall rules to limit inbound traffic to router management interfaces. 7) Regularly review router logs for signs of exploitation attempts. These steps go beyond generic advice by focusing on immediate containment and detection in the absence of a patch.