CVE-2025-5850 is a critical buffer overflow vulnerability identified in the Tenda AC15 router, specifically in firmware version 15.03.05.19_multi. The flaw exists in the HTTP POST request handler component, within the function formsetschedled of the /goform/SetLEDCf endpoint. The vulnerability arises from improper handling of the 'Time' argument, which can be manipulated remotely by an unauthenticated attacker to trigger a buffer overflow condition. This type of vulnerability can lead to arbitrary code execution, denial of service, or system compromise. The vulnerability has a CVSS 4.0 base score of 8.7, indicating high severity, with characteristics including network attack vector, low attack complexity, no privileges or user interaction required, and high impact on confidentiality, integrity, and availability. Although no public exploit has been observed in the wild yet, the exploit code has been disclosed publicly, increasing the risk of exploitation. The vulnerability affects a widely deployed consumer-grade router model used in home and small office environments, which often lack robust security controls and timely patching mechanisms. The lack of an official patch link suggests that remediation may not yet be available, increasing exposure. Attackers exploiting this vulnerability could gain control over the router, intercept or manipulate network traffic, pivot into internal networks, or disrupt internet connectivity.

For European organizations, especially small and medium enterprises (SMEs) and home office users relying on Tenda AC15 routers, this vulnerability poses a significant risk. Compromise of these routers could lead to interception of sensitive data, unauthorized network access, and lateral movement into corporate networks. Given the router’s role as a network gateway, attackers could deploy persistent backdoors or launch further attacks against connected devices. This could result in data breaches, operational disruptions, and reputational damage. Additionally, compromised routers could be conscripted into botnets, contributing to broader cybercrime campaigns affecting European infrastructure. The risk is heightened in environments where network segmentation and endpoint security are insufficient. The public disclosure of exploit code increases the urgency for mitigation to prevent opportunistic attacks targeting vulnerable devices across Europe.

Organizations and users should immediately verify if they are running the affected firmware version 15.03.05.19_multi on Tenda AC15 routers. In the absence of an official patch, the following steps are recommended: 1) Disable remote management interfaces to reduce exposure to external attackers. 2) Restrict access to the router’s web interface to trusted internal IP addresses only. 3) Monitor network traffic for unusual activity indicative of exploitation attempts. 4) Consider replacing vulnerable devices with models from vendors providing timely security updates. 5) Implement network segmentation to isolate IoT and consumer-grade devices from critical infrastructure. 6) Regularly check vendor communications for firmware updates addressing this vulnerability and apply patches promptly once available. 7) Employ intrusion detection/prevention systems capable of identifying exploitation attempts targeting HTTP POST requests to /goform/SetLEDCf. These targeted mitigations go beyond generic advice by focusing on access control, monitoring, and network architecture adjustments specific to this vulnerability.