CVE-2025-12236 is a buffer overflow vulnerability identified in the Tenda CH22 router firmware version 1.0.0.1. The vulnerability resides in the fromDhcpListClient function within the /goform/DhcpListClient endpoint, where improper handling of the 'page' argument allows an attacker to overflow a buffer. This flaw can be exploited remotely over the network without requiring user interaction or elevated privileges, making it highly accessible to attackers. The buffer overflow could enable arbitrary code execution, potentially allowing attackers to take full control of the affected device, disrupt network operations, or pivot into internal networks. The vulnerability has been assigned a CVSS 4.0 base score of 8.7, indicating high severity due to its network attack vector, low complexity, no required privileges or user interaction, and high impact on confidentiality, integrity, and availability. Although no known exploits are currently active in the wild, the public disclosure of the vulnerability increases the likelihood of exploitation attempts. The lack of available patches at the time of disclosure necessitates immediate mitigation efforts by affected organizations. The Tenda CH22 is typically used in small office and home office environments, but its compromise could have cascading effects if deployed in enterprise or critical infrastructure settings.

For European organizations, exploitation of CVE-2025-12236 could lead to severe consequences including unauthorized access to sensitive network traffic, disruption of network services, and potential lateral movement within corporate networks. The ability to execute arbitrary code remotely without authentication means attackers could deploy malware, establish persistent backdoors, or exfiltrate data. This poses a significant risk to confidentiality, integrity, and availability of organizational IT assets. Critical infrastructure sectors such as energy, healthcare, and telecommunications that rely on Tenda CH22 devices for network connectivity could experience operational disruptions or data breaches. Additionally, the widespread use of Tenda devices in small and medium enterprises across Europe increases the attack surface, potentially enabling attackers to leverage compromised devices as entry points into larger networks. The public disclosure without an immediate patch increases the urgency for organizations to implement compensating controls to reduce exposure.

1. Immediate network segmentation: Isolate Tenda CH22 devices from critical network segments to limit potential lateral movement if compromised. 2. Access control: Restrict access to the /goform/DhcpListClient endpoint by implementing firewall rules or access control lists that block unauthorized external and internal access. 3. Monitor network traffic: Deploy intrusion detection/prevention systems (IDS/IPS) to detect anomalous activity targeting the vulnerable endpoint or unusual DHCP client list requests. 4. Vendor engagement: Regularly check for firmware updates or security advisories from Tenda and apply patches promptly once available. 5. Device replacement: For high-risk environments, consider replacing Tenda CH22 devices with alternatives that have no known vulnerabilities or better security track records. 6. Incident response readiness: Prepare for potential exploitation by updating incident response plans to include detection and remediation steps specific to this vulnerability. 7. User awareness: Educate network administrators about the vulnerability and the importance of restricting device management interfaces to trusted personnel only.