CVE-2026-4534 is a stack-based buffer overflow vulnerability identified in the Tenda FH451 router firmware version 1.0.0.9. The vulnerability resides in the formWrlExtraSet function, specifically in the handling of the GO argument passed to the /goform/WrlExtraSet endpoint. An attacker can remotely send a specially crafted request to this endpoint, causing a stack overflow due to improper bounds checking or input validation. This overflow can overwrite the stack, potentially allowing arbitrary code execution with elevated privileges on the device. The vulnerability is remotely exploitable without requiring user interaction or prior authentication, making it highly accessible to attackers. The CVSS 4.0 base score is 8.7, reflecting high severity with network attack vector, low complexity, no privileges required, and no user interaction needed. The impact includes full compromise of the router, enabling attackers to intercept, modify, or disrupt network traffic, install persistent malware, or pivot into internal networks. Although no active exploitation has been reported, a public exploit is available, increasing the likelihood of attacks. The lack of an official patch at the time of disclosure necessitates immediate mitigation efforts by affected users and organizations.

The exploitation of CVE-2026-4534 can have severe consequences for organizations worldwide. Compromise of Tenda FH451 routers can lead to unauthorized access to internal networks, interception of sensitive data, and disruption of network services. Attackers gaining control over these routers can manipulate traffic, conduct man-in-the-middle attacks, or launch further attacks against connected devices. This can result in data breaches, loss of confidentiality, integrity violations, and denial of service. Given that routers are critical infrastructure components, their compromise undermines overall network security posture and can facilitate lateral movement within corporate or home networks. The availability of a public exploit increases the risk of widespread attacks, especially targeting unpatched devices. Organizations relying on Tenda FH451 devices in their network infrastructure face elevated risks of operational disruption and data compromise.

1. Immediate mitigation should focus on isolating affected Tenda FH451 devices from untrusted networks to reduce exposure. 2. Monitor network traffic for unusual activity or attempts to access the /goform/WrlExtraSet endpoint. 3. Implement network segmentation to limit the impact of a compromised router. 4. Apply any available firmware updates or patches from Tenda as soon as they are released. 5. If patches are unavailable, consider replacing affected devices with alternative hardware from vendors with timely security support. 6. Employ intrusion detection/prevention systems (IDS/IPS) with signatures targeting this specific exploit to detect and block exploitation attempts. 7. Restrict remote management access to trusted IP addresses only and disable remote administration if not required. 8. Regularly audit router configurations and logs for signs of compromise. 9. Educate network administrators about this vulnerability and the importance of timely patching and monitoring. 10. Maintain an incident response plan to quickly address any detected exploitation.