CVE-2026-3811 is a stack-based buffer overflow vulnerability identified in the Tenda FH1202 router firmware version 1.2.0.14(408). The flaw resides in the fromP2pListFilter function, specifically within the /goform/P2pListFilter endpoint, which processes the 'page' argument. Improper validation or bounds checking of this argument allows an attacker to overflow the stack buffer, potentially overwriting return addresses or control data. This can lead to arbitrary code execution or cause the device to crash, resulting in denial of service. The vulnerability is remotely exploitable over the network without requiring authentication or user interaction, making it highly accessible to attackers. The CVSS v4.0 score of 8.7 reflects the critical nature of the flaw, with high impact on confidentiality, integrity, and availability. Although no confirmed exploits in the wild have been reported, the public disclosure of exploit code increases the likelihood of attacks. The affected product, Tenda FH1202, is a consumer-grade wireless router commonly used in residential and small office environments, which may lack robust security monitoring. The absence of an official patch link suggests that mitigation options may be limited or pending from the vendor. Attackers exploiting this vulnerability could gain control over the device, intercept or manipulate network traffic, or disrupt network connectivity.

The impact of CVE-2026-3811 is significant for organizations and individuals using the Tenda FH1202 router. Successful exploitation can lead to full compromise of the device, allowing attackers to execute arbitrary code with elevated privileges. This can result in unauthorized access to internal networks, interception of sensitive data, and manipulation or disruption of network communications. The denial of service caused by crashes can interrupt business operations or home network availability. Since the vulnerability is remotely exploitable without authentication, it poses a high risk of widespread attacks, especially in environments where these routers are exposed to untrusted networks or the internet. Compromised routers can also be leveraged as entry points for lateral movement within corporate networks or as part of botnets for broader cyberattacks. The lack of immediate patches increases the window of exposure, making timely mitigation critical.

To mitigate CVE-2026-3811, organizations should first check for any official firmware updates or patches released by Tenda and apply them promptly once available. In the absence of patches, network administrators should restrict access to the router's management interfaces by implementing firewall rules to block inbound traffic to the /goform/P2pListFilter endpoint from untrusted networks. Disabling remote management features or restricting them to trusted IP addresses can reduce exposure. Network segmentation should be employed to isolate vulnerable devices from critical infrastructure. Monitoring network traffic for unusual activity targeting the router can help detect exploitation attempts. Additionally, replacing affected devices with models from vendors with timely security support should be considered for long-term risk reduction. Users should also change default credentials and ensure strong passwords to prevent secondary attacks. Regular backups of router configurations are recommended to facilitate recovery if compromise occurs.