CVE-2025-5685 is a critical stack-based buffer overflow vulnerability identified in the Tenda CH22 router, specifically version 1.0.0.1. The flaw resides in the function formNatlimit within the /goform/Natlimit endpoint. An attacker can manipulate the 'page' argument passed to this function, causing a stack-based buffer overflow. This type of vulnerability allows an attacker to overwrite the stack memory, potentially leading to arbitrary code execution, denial of service, or system compromise. The vulnerability is remotely exploitable without requiring user interaction or authentication, which significantly increases its risk profile. The CVSS 4.0 score of 8.7 (high severity) reflects the ease of exploitation (network attack vector, low complexity) and the high impact on confidentiality, integrity, and availability. Although no public exploits are currently known to be actively used in the wild, the disclosure of the exploit code means that threat actors could develop and deploy attacks rapidly. The vulnerability affects a specific firmware version (1.0.0.1) of the Tenda CH22 router, a device commonly used in small office and home office environments for network connectivity. Given the nature of the vulnerability, successful exploitation could allow attackers to gain control over the router, intercept or manipulate network traffic, or pivot into internal networks.

For European organizations, this vulnerability poses a significant risk, especially for small and medium enterprises (SMEs) and home office users relying on Tenda CH22 routers. Compromise of these routers could lead to unauthorized access to internal networks, interception of sensitive data, and disruption of business operations. The ability to execute code remotely without authentication means attackers can target vulnerable devices en masse, potentially leading to widespread network outages or use of compromised routers as footholds for further attacks. Critical infrastructure and organizations with remote workforces are particularly at risk if these routers are deployed at network edges. Additionally, the compromise of routers can facilitate man-in-the-middle attacks, data exfiltration, and lateral movement within corporate networks, amplifying the impact on confidentiality and integrity of organizational data.

Given the absence of an official patch link, immediate mitigation should focus on network-level controls and configuration changes. Organizations should: 1) Identify and inventory all Tenda CH22 devices running firmware version 1.0.0.1. 2) Restrict remote access to the router management interfaces, especially the /goform/Natlimit endpoint, by implementing firewall rules that limit access to trusted IP addresses only. 3) Disable remote management features if not required. 4) Monitor network traffic for unusual activity or attempts to exploit the /goform/Natlimit endpoint. 5) Employ intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics targeting buffer overflow attempts on Tenda routers. 6) Contact Tenda support or monitor official channels for firmware updates or patches addressing this vulnerability and apply them promptly once available. 7) Consider replacing vulnerable devices with models that have active security support if patches are delayed. 8) Educate users and IT staff about the risks and signs of router compromise to enable rapid detection and response.