CVE-2025-63459 is a stack overflow vulnerability identified in the Totolink A7000R router firmware version 9.1.0u.6115_B20201022. The vulnerability resides in the sub_421CF0 function, specifically in the processing of the ssid5g parameter. When an attacker sends a crafted request containing a maliciously crafted ssid5g parameter, it causes a stack overflow condition. This overflow can lead to a Denial of Service (DoS) by crashing or destabilizing the router, thereby interrupting network services. The vulnerability does not require prior authentication, meaning it can be exploited remotely by anyone able to send requests to the router’s management interface or exposed services. No public exploits or proof-of-concept code have been reported yet, and no official patches or updates have been released by the vendor. The lack of a CVSS score indicates that the vulnerability is newly published and not yet fully assessed. The primary impact is on availability, as the stack overflow leads to service disruption rather than direct code execution or data compromise. However, the potential for further exploitation cannot be ruled out if attackers develop more advanced payloads. The affected device is a consumer-grade or small office/home office (SOHO) router, which may be deployed in various organizational environments. Attackers exploiting this vulnerability could cause network outages, impacting business operations and connectivity.

For European organizations, exploitation of CVE-2025-63459 could result in significant network disruptions due to router crashes or reboots caused by the stack overflow. This would affect the availability of network services, potentially halting business operations reliant on internet connectivity or internal network access. Organizations using Totolink A7000R routers in critical roles such as branch office connectivity, remote access, or as part of network infrastructure could experience downtime. The impact is primarily on availability rather than confidentiality or integrity. Given that the vulnerability can be triggered remotely without authentication, attackers could launch DoS attacks from outside the network if the router’s management interfaces are exposed to the internet or from within the network if internal systems are compromised. This could also be leveraged as part of a larger attack chain to disrupt operations or distract security teams. The absence of known exploits reduces immediate risk, but the vulnerability should be treated seriously due to the ease of exploitation and potential operational impact.

1. Immediately restrict access to the router’s management interfaces by implementing strict firewall rules and network segmentation to limit exposure to trusted administrators only. 2. Disable remote management features unless absolutely necessary, and if enabled, restrict access to specific IP addresses or VPN connections. 3. Monitor network traffic for unusual or malformed requests targeting the ssid5g parameter or router management endpoints, using intrusion detection/prevention systems (IDS/IPS). 4. Maintain an inventory of all Totolink A7000R devices within the organization to identify potentially vulnerable units. 5. Engage with the vendor for firmware updates or patches addressing this vulnerability and apply them promptly once available. 6. Consider replacing affected devices with alternative routers that have a stronger security track record if patching is delayed. 7. Educate network administrators about the vulnerability and signs of exploitation to improve detection and response capabilities. 8. Implement network redundancy to minimize operational impact in case of device failure due to exploitation.