CVE-2025-63459 is a stack overflow vulnerability identified in the Totolink A7000R router firmware version 9.1.0u.6115_B20201022. The vulnerability arises from improper bounds checking in the processing of the ssid5g parameter within the sub_421CF0 function. An attacker can craft a malicious network request that overflows the stack buffer, leading to memory corruption. The primary impact is a Denial of Service (DoS), where the router crashes or becomes unresponsive, disrupting network connectivity. The vulnerability is remotely exploitable without any authentication or user interaction, increasing its risk profile. The Common Weakness Enumeration (CWE) classification is CWE-121, indicating a classic stack-based buffer overflow. 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 patches or exploits have been publicly disclosed yet, but the vulnerability's presence in a widely deployed consumer and small business router model makes it a notable threat. Attackers could leverage this to cause outages in home or small office networks, potentially impacting business operations or critical services relying on these devices.

For European organizations, the primary impact of CVE-2025-63459 is the potential for network disruption due to Denial of Service conditions on affected Totolink A7000R routers. This can lead to loss of internet connectivity, interruption of business-critical applications, and degraded operational efficiency. Small and medium enterprises (SMEs) and home offices using this router model are particularly vulnerable, as they may lack robust network monitoring and rapid incident response capabilities. Critical infrastructure sectors relying on these devices for network access could face operational interruptions, affecting services such as remote work, communications, and data transfers. Additionally, the lack of authentication for exploitation means attackers can target devices en masse, increasing the risk of widespread outages. Although no data confidentiality or integrity impact is reported, availability loss alone can have significant financial and reputational consequences. The absence of known exploits currently provides a window for mitigation, but the vulnerability’s characteristics suggest it could be weaponized in the future.

1. Immediately inventory and identify all Totolink A7000R routers in use within the organization. 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 systems and sensitive data. 4. Employ firewall rules to restrict inbound traffic to management interfaces and block unsolicited requests targeting the ssid5g parameter. 5. Use intrusion detection/prevention systems (IDS/IPS) with custom signatures to detect anomalous packets that may exploit this stack overflow. 6. Consider replacing affected routers with alternative models that have a stronger security posture if patching is delayed. 7. Educate network administrators about this vulnerability to ensure rapid detection and response to any signs of exploitation. 8. Regularly back up router configurations and maintain incident response plans to quickly recover from potential DoS events.