CVE-2026-3398 is a buffer overflow vulnerability identified in the Tenda F453 router firmware version 1.0.0.3. The vulnerability resides in the fromAdvSetWan function within the httpd service, which processes the /goform/AdvSetWan endpoint. Specifically, improper handling of the wanmode/PPPOEPassword parameter allows an attacker to overflow a buffer remotely. This flaw can be exploited without authentication or user interaction, making it highly accessible to remote attackers. The buffer overflow can lead to arbitrary code execution or cause the device to crash, impacting confidentiality, integrity, and availability of the affected device. The vulnerability has a CVSS 4.0 base score of 8.7, reflecting its high severity due to network attack vector, low complexity, no privileges or user interaction required, and high impact on all security properties. Although no exploits are currently observed in the wild, the public disclosure of exploit code increases the likelihood of exploitation attempts. The affected device, Tenda F453, is a consumer-grade router commonly used in home and small office environments, which could be targeted to gain network access or disrupt connectivity. The lack of available patches at the time of disclosure necessitates immediate mitigation efforts to reduce exposure.

The impact of CVE-2026-3398 is significant for organizations and individuals using the Tenda F453 router. Successful exploitation can lead to remote code execution, allowing attackers to take full control of the device, manipulate network traffic, intercept sensitive data, or launch further attacks within the internal network. The buffer overflow can also cause denial of service by crashing the router, disrupting internet connectivity and business operations. Since the vulnerability requires no authentication or user interaction, it can be exploited by attackers scanning for vulnerable devices exposed to the internet. This increases the risk of widespread attacks, especially in environments where Tenda routers are deployed without proper network segmentation or firewall protections. The compromise of these routers could lead to data breaches, espionage, or serve as a foothold for lateral movement in targeted attacks. The absence of patches at disclosure time further elevates the risk, making timely mitigation critical to prevent exploitation.

1. Immediately restrict remote management access to the Tenda F453 router by disabling WAN-side administration or limiting it to trusted IP addresses. 2. Implement network segmentation to isolate vulnerable routers from critical internal systems and sensitive data. 3. Monitor network traffic for unusual patterns or attempts to access the /goform/AdvSetWan endpoint with suspicious parameters. 4. Deploy intrusion detection/prevention systems (IDS/IPS) with signatures targeting attempts to exploit this specific buffer overflow. 5. Regularly check for and apply firmware updates from Tenda as soon as a patch addressing CVE-2026-3398 becomes available. 6. If patching is not immediately possible, consider replacing affected devices with models from vendors with timely security support. 7. Educate users and administrators about the risks of exposing router management interfaces to the internet. 8. Conduct periodic vulnerability scans to identify exposed Tenda F453 devices within the network or on the public internet.