CVE-2025-4850 is a command injection vulnerability identified in the TOTOLINK N300RH router, specifically affecting firmware version 6.1c.1390_B20191101. The vulnerability resides in the setUnloadUserData function within the /cgi-bin/cstecgi.cgi endpoint. An attacker can manipulate the 'plugin_name' argument to inject arbitrary commands that the device executes. This vulnerability is remotely exploitable without requiring user interaction or prior authentication, increasing its risk profile. The CVSS 4.0 base score is 5.3, indicating a medium severity level, primarily due to the requirement of low privileges (PR:L) and limited impact on confidentiality, integrity, and availability (VC:L, VI:L, VA:L). The vulnerability does not require user interaction (UI:N) and can be exploited over the network (AV:N). Although no known exploits are currently reported in the wild, the public disclosure of the exploit code increases the likelihood of exploitation attempts. The vulnerability could allow attackers to execute arbitrary commands on the device, potentially leading to unauthorized control, data leakage, or disruption of network services. The lack of available patches or mitigation guidance from the vendor at this time further exacerbates the risk for affected users.

For European organizations, the exploitation of CVE-2025-4850 could lead to significant security risks, especially for those relying on TOTOLINK N300RH routers in their network infrastructure. Successful exploitation could allow attackers to gain control over the router, enabling interception or manipulation of network traffic, deployment of further malware, or pivoting into internal networks. This could compromise confidentiality of sensitive data, integrity of communications, and availability of network services. Small and medium enterprises (SMEs) and home office environments using this device are particularly vulnerable due to typically less rigorous network security controls. Additionally, critical infrastructure or organizations with remote sites using these routers could face operational disruptions. The medium CVSS score suggests that while the impact is not catastrophic, the ease of remote exploitation without authentication makes it a credible threat that should be addressed promptly to avoid escalation.

1. Immediate mitigation should include isolating affected TOTOLINK N300RH devices from critical network segments to limit potential lateral movement. 2. Network administrators should monitor network traffic for unusual patterns or command injection attempts targeting /cgi-bin/cstecgi.cgi endpoints. 3. Implement network-level access controls such as firewall rules to restrict access to router management interfaces from untrusted networks. 4. If possible, disable or restrict access to the vulnerable setUnloadUserData function or the entire CGI interface until a vendor patch is available. 5. Regularly update firmware when TOTOLINK releases a security patch addressing this vulnerability. 6. Employ network intrusion detection/prevention systems (IDS/IPS) with signatures to detect exploitation attempts. 7. Conduct thorough audits of router configurations and logs to identify any signs of compromise. 8. Educate IT staff about this vulnerability and ensure incident response plans include steps for router compromise scenarios.