CVE-2025-45789 is a medium-severity buffer overflow vulnerability identified in the TOTOLINK A3100R router firmware version 5.9c.1527. The vulnerability arises from improper handling of the urlKeyword parameter within the setParentalRules function. Specifically, the buffer overflow (CWE-121) occurs when the input to urlKeyword exceeds the allocated buffer size, leading to memory corruption. This flaw can be exploited remotely over the network without requiring authentication or user interaction, as indicated by the CVSS vector (AV:N/AC:L/PR:N/UI:N). Successful exploitation could allow an attacker to overwrite adjacent memory, potentially leading to partial compromise of confidentiality and integrity of the device. However, the CVSS score of 6.5 suggests that the impact on availability is minimal or not affected. No known public exploits are currently reported, and no patches have been linked yet. The vulnerability was reserved and published in April and May 2025 respectively, with enrichment from CISA, indicating recognition by US cybersecurity authorities. The TOTOLINK A3100R is a consumer-grade wireless router, and exploitation could enable attackers to manipulate parental control settings or execute arbitrary code, potentially pivoting into the internal network or intercepting traffic.

For European organizations, the impact of this vulnerability depends on the deployment of TOTOLINK A3100R routers within their networks. While primarily a consumer device, some small businesses or branch offices might use this router model due to cost considerations. Exploitation could allow attackers to gain unauthorized access to network traffic or alter router configurations, undermining network security and data confidentiality. This is particularly concerning for organizations handling sensitive personal data under GDPR, as unauthorized access could lead to data breaches and regulatory penalties. Additionally, compromised routers could be leveraged as entry points for lateral movement or as part of botnets, affecting overall network availability indirectly. The lack of authentication requirement increases the risk, especially if routers are exposed to the internet or poorly segmented from critical infrastructure. However, the absence of known exploits and the medium severity rating somewhat limit immediate widespread impact.

Organizations and users should first verify if they are using the TOTOLINK A3100R router with firmware version 5.9c.1527. Given the absence of an official patch, immediate mitigation steps include restricting remote access to the router's management interface by disabling WAN-side administration and ensuring the device is not directly exposed to the internet. Network segmentation should be enforced to isolate the router from sensitive internal systems. Monitoring network traffic for unusual activity related to parental control settings or unexpected configuration changes can help detect exploitation attempts. Users should also consider upgrading to newer firmware versions once available or replacing the device with a more secure alternative. Implementing strict firewall rules and using VPNs for remote access can further reduce exposure. Regularly checking vendor advisories and subscribing to vulnerability notifications is recommended to apply patches promptly when released.