CVE-2025-60685 is a stack-based buffer overflow vulnerability identified in the ToToLink A720R Router firmware version V4.1.5cu.614_B20230630, specifically within the sysconf binary's sub_401EE0 function. The vulnerability stems from the way the sysconf binary reads and parses the /proc/stat file. The binary uses fgets() to read lines from /proc/stat into a local buffer, then uses sscanf() with the %s format specifier to parse the line into a single-byte variable. This mismatch leads to a buffer overflow on the stack because the %s specifier expects a string but is assigned to a single-byte variable, allowing adjacent stack memory to be overwritten. An attacker who has filesystem write privileges on the device can craft malicious content in /proc/stat to trigger this overflow, potentially leading to arbitrary code execution. The vulnerability requires local access with write permissions to the filesystem, no authentication or user interaction is necessary. The CVSS v3.1 score is 5.1 (medium), reflecting the limited attack vector (local) and privileges required, but the potential impact includes confidentiality loss and availability disruption. No patches or known exploits are currently reported, but the vulnerability is classified under CWE-121 (stack-based buffer overflow), a common and dangerous class of vulnerabilities. This flaw could be exploited to gain control over the router, enabling attackers to manipulate network traffic, disrupt services, or pivot into internal networks.

For European organizations, exploitation of CVE-2025-60685 could lead to unauthorized control over affected ToToLink A720R routers, compromising network security and potentially allowing attackers to intercept, modify, or disrupt network traffic. This can impact confidentiality by exposing sensitive data traversing the network and availability by causing router crashes or service interruptions. Given the router's role in network infrastructure, successful exploitation could facilitate lateral movement within corporate networks or critical infrastructure environments. The requirement for filesystem write privileges limits the attack surface primarily to insiders or attackers who have already gained some level of access, but the lack of authentication or user interaction requirements lowers barriers once local access is obtained. European organizations relying on these routers in office environments, small to medium enterprises, or critical infrastructure sectors could face operational disruptions and data breaches if this vulnerability is exploited.

1. Restrict filesystem write permissions on the router to trusted users and processes only, minimizing the risk of malicious /proc/stat manipulation. 2. Implement strict network segmentation and access controls to prevent unauthorized local access to the router's filesystem. 3. Monitor router logs and filesystem integrity for unusual changes to /proc/stat or other critical system files. 4. Deploy host-based intrusion detection systems (HIDS) on network management stations to detect anomalous activities related to router management. 5. Engage with ToToLink or authorized vendors to obtain firmware updates or patches addressing this vulnerability as soon as they become available. 6. If firmware updates are delayed, consider temporary mitigations such as disabling or restricting access to the sysconf binary or related management interfaces. 7. Conduct regular security audits and penetration testing focusing on router configurations and local access controls. 8. Educate network administrators about the risks of local privilege escalation and the importance of maintaining strict access controls on network devices.