CVE-2026-3811 is a stack-based buffer overflow vulnerability identified in the Tenda FH1202 router firmware version 1.2.0.14(408). The vulnerability exists in the fromP2pListFilter function, which processes requests to the /goform/P2pListFilter endpoint. Specifically, the 'page' parameter is improperly validated, allowing an attacker to supply crafted input that overflows the stack buffer. This overflow 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 dangerous. The CVSS 4.0 vector indicates network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:L), no user interaction (UI:N), and high impact on confidentiality, integrity, and availability (VC:H, VI:H, VA:H). While no confirmed exploits in the wild have been reported, the public availability of exploit code increases the risk of imminent attacks. The affected product is a widely deployed consumer-grade router, often used in home and small office environments, which may lack robust security monitoring. No official patches or mitigation links have been provided yet, emphasizing the need for immediate defensive measures.

The vulnerability poses a severe risk to organizations and individuals using the Tenda FH1202 router with the specified firmware. Successful exploitation can lead to complete compromise of the device, allowing attackers to execute arbitrary code, potentially gaining control over the network gateway. This can result in interception or manipulation of network traffic, unauthorized access to internal systems, and disruption of internet connectivity. The denial of service impact can cause network outages affecting business operations or critical communications. Since the exploit requires no authentication or user interaction, attackers can scan and target vulnerable devices en masse, increasing the scale of potential attacks. The exposure is particularly critical for small businesses and home users who may not have advanced security controls or timely patching processes. Additionally, compromised routers can be leveraged as entry points for further attacks or as part of botnets for distributed denial of service (DDoS) campaigns.

1. Immediate mitigation should include isolating the affected Tenda FH1202 devices from untrusted networks to reduce exposure. 2. Monitor network traffic for unusual activity originating from or targeting these routers, including scanning attempts or exploitation signatures. 3. Disable remote management features if enabled, especially those accessible from the internet. 4. Implement network segmentation to limit the impact of a compromised router on critical systems. 5. Regularly check for firmware updates from Tenda and apply patches as soon as they become available. 6. If official patches are delayed, consider replacing affected devices with models from vendors with more timely security support. 7. Employ intrusion detection/prevention systems (IDS/IPS) with signatures for this vulnerability once available. 8. Educate users about the risks of using outdated firmware and encourage routine device maintenance. 9. Use network access controls to restrict administrative access to trusted hosts only. 10. Conduct vulnerability scans to identify all devices running the vulnerable firmware version to prioritize remediation.