CVE-2026-2185 is a critical stack-based buffer overflow vulnerability identified in the Tenda RX3 router firmware version 16.03.13.11. The flaw exists in the MAC Filtering Configuration Endpoint, specifically within the set_device_name function located in the /goform/setBlackRule path. This function improperly processes the devName/mac parameter, allowing an attacker to supply crafted input that overflows the stack buffer. The overflow can corrupt adjacent memory, potentially enabling arbitrary code execution or denial of service. The vulnerability is remotely exploitable without requiring authentication or user interaction, making it highly accessible to attackers. The CVSS 4.0 score of 8.7 reflects the vulnerability's high impact on confidentiality, integrity, and availability, with low attack complexity and no privileges required. Although no active exploitation has been reported, a public exploit is available, increasing the risk of imminent attacks. The vulnerability affects a widely deployed consumer and small business router model, which often serves as a network gateway, amplifying the potential impact. The absence of an official patch at the time of disclosure necessitates immediate mitigation efforts to prevent exploitation.

For European organizations, this vulnerability presents a significant threat to network security and operational continuity. Exploitation could allow attackers to execute arbitrary code on the router, leading to full device compromise. This can result in interception or manipulation of network traffic, unauthorized access to internal networks, and disruption of internet connectivity. Critical infrastructure, SMEs, and home office environments using Tenda RX3 routers are particularly vulnerable. The compromise of these devices could facilitate lateral movement within corporate networks or serve as a foothold for further attacks. Given the remote exploitability without authentication, attackers can target vulnerable devices en masse, potentially causing widespread outages or data breaches. The impact on confidentiality, integrity, and availability is high, threatening sensitive data and network reliability across affected organizations.

Immediate mitigation steps include isolating affected Tenda RX3 devices from critical network segments and restricting remote management access. Network administrators should implement strict firewall rules to block incoming traffic to the /goform/setBlackRule endpoint or disable MAC filtering features if feasible. Monitoring network traffic for anomalous requests targeting this endpoint can help detect exploitation attempts. Until an official firmware patch is released, organizations should consider replacing vulnerable devices with models from vendors with timely security updates. Employing network segmentation and intrusion detection systems can limit the impact of a compromised router. Additionally, educating users about the risks and ensuring that default credentials are changed reduces the attack surface. Regularly checking vendor advisories for patches and applying them promptly once available is critical to long-term remediation.