CVE-2025-63154 is a stack overflow vulnerability identified in the TOTOLink A7000R router firmware version V9.1.0u.6115_B20201022. The vulnerability resides specifically in the handling of the addEffect parameter within the urldecode function, which processes URL-encoded data. An attacker can craft a malicious POST request containing a specially designed payload in the addEffect parameter that triggers a stack overflow condition. This overflow can cause the router's process to crash, leading to a Denial of Service (DoS) by making the device unresponsive or rebooting it unexpectedly. The vulnerability does not require authentication or user interaction, meaning it can be exploited remotely by any attacker who can send HTTP POST requests to the device's management interface or exposed services. No CVSS score has been assigned yet, and no patches or known exploits have been publicly disclosed. However, the nature of the vulnerability implies that it could be leveraged to disrupt network connectivity, affecting the availability of services relying on the affected routers. The TOTOLink A7000R is a consumer and small business router, and its presence in European networks, especially in small offices or home office environments, could lead to localized network outages if exploited. The lack of authentication requirements increases the risk profile, as attackers do not need credentials to trigger the DoS. The vulnerability highlights the importance of secure input validation and memory management in embedded network devices.

For European organizations, exploitation of CVE-2025-63154 could result in temporary loss of network connectivity due to router crashes, impacting business operations, remote work capabilities, and access to cloud services. Small and medium enterprises (SMEs) and home office setups using TOTOLink A7000R routers are particularly vulnerable, as these devices often lack advanced security monitoring. Critical infrastructure sectors relying on these routers for network access could experience service interruptions, potentially affecting operational technology systems or communication channels. The DoS nature of the vulnerability does not directly compromise confidentiality or integrity but can cause significant availability issues. In environments with limited IT support, recovery from such outages may be delayed, amplifying the impact. Additionally, attackers could use this vulnerability as part of a broader attack chain to disrupt organizational networks or as a distraction while conducting other malicious activities. The absence of known exploits currently reduces immediate risk but does not eliminate the threat, especially as exploit code could be developed following public disclosure.

Organizations should immediately inventory their network devices to identify any TOTOLink A7000R routers running the vulnerable firmware version V9.1.0u.6115_B20201022. Until a vendor patch is released, network administrators should implement strict access controls to limit exposure of router management interfaces to untrusted networks, ideally restricting access to internal trusted IP ranges only. Deploy web application firewalls (WAFs) or intrusion prevention systems (IPS) capable of detecting and blocking anomalous HTTP POST requests targeting the addEffect parameter or unusual URL-encoded payloads. Network segmentation can isolate vulnerable devices from critical infrastructure and sensitive data environments to reduce potential impact. Monitoring network traffic for repeated POST requests or unusual patterns directed at router interfaces can provide early detection of exploitation attempts. Organizations should engage with TOTOLink support channels to obtain firmware updates or advisories and apply patches promptly once available. Additionally, consider replacing vulnerable devices with models from vendors with stronger security track records if patching is delayed. Employee awareness about reporting network disruptions can also aid in rapid incident response.