CVE-2025-63461 identifies a stack-based buffer overflow vulnerability in the Totolink A7000R router firmware version 9.1.0u.6115_B20201022. The vulnerability arises from improper handling of the ssid5g parameter within the urldecode function, which fails to adequately validate or limit input size. When an attacker sends a specially crafted HTTP request containing an oversized or malformed ssid5g parameter, the stack overflow occurs, leading to memory corruption. This corruption results in a denial of service condition by crashing or rebooting the router, thereby disrupting network availability. The vulnerability is remotely exploitable without authentication or user interaction, increasing its risk profile. The CVSS v3.1 base score is 7.5, reflecting high severity due to network attack vector, low attack complexity, no privileges required, no user interaction, and impact limited to availability (no confidentiality or integrity loss). No patches or official fixes have been published yet, and no exploits have been observed in the wild. The underlying weakness corresponds to CWE-121 (Stack-based Buffer Overflow), a common and critical software flaw that can lead to crashes or potential code execution in other contexts. Given the router's role as a network gateway, successful exploitation can cause significant service disruption.

For European organizations, exploitation of CVE-2025-63461 could lead to denial of service on critical network infrastructure, causing outages in internet connectivity or internal network segments. This can disrupt business operations, remote work capabilities, and access to cloud services. Organizations relying on Totolink A7000R routers in office environments, small to medium enterprises, or branch offices may face network downtime until the device is rebooted or replaced. The lack of confidentiality or integrity impact limits data breach risks, but availability loss can affect productivity and service delivery. Critical sectors such as finance, healthcare, and government agencies using these routers could experience operational interruptions. Additionally, attackers could leverage the DoS as a diversion while conducting other attacks. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially if automated scanning tools identify vulnerable devices.

1. Immediately restrict external network access to the router's management interfaces to prevent remote exploitation. 2. Monitor Totolink's official channels for firmware updates addressing this vulnerability and apply patches promptly once available. 3. Implement network segmentation to isolate vulnerable routers from critical infrastructure and sensitive systems. 4. Employ intrusion detection or prevention systems (IDS/IPS) to detect anomalous or malformed HTTP requests targeting the ssid5g parameter. 5. Conduct regular vulnerability scans to identify devices running the affected firmware version. 6. Where possible, replace Totolink A7000R routers with alternative models that have no known vulnerabilities or have received security updates. 7. Educate network administrators about this vulnerability and ensure incident response plans include steps for router-related DoS events. 8. Limit the exposure of management interfaces to trusted internal networks only, using VPNs or secure tunnels for remote access.