CVE-2026-2877 is a stack-based buffer overflow vulnerability identified in the Tenda A18 router firmware version 15.13.07.13. The vulnerability arises from improper handling of input in the strcpy function used in the /goform/WifiExtraSet endpoint of the embedded Httpd service. Specifically, the argument wpapsk_crypto5g is not properly bounded, allowing an attacker to overflow the stack buffer by sending a crafted HTTP request. This overflow can overwrite the return address or other control data on the stack, enabling remote code execution with elevated privileges on the device. The vulnerability requires no authentication and no user interaction, making it remotely exploitable over the network. The CVSS v4.0 base score is 8.7, reflecting high severity due to the ease of exploitation and the critical impact on device security. Although no known exploits are currently active in the wild, the public disclosure of exploit details increases the likelihood of exploitation attempts. The vulnerability affects the confidentiality, integrity, and availability of the router, potentially allowing attackers to intercept or manipulate network traffic, disrupt service, or use the device as a foothold for further attacks within the network. No official patches or mitigations have been linked yet, emphasizing the need for immediate defensive actions by users and administrators.

The impact of CVE-2026-2877 is significant for organizations relying on Tenda A18 routers. Successful exploitation can lead to complete compromise of the affected device, allowing attackers to execute arbitrary code with system-level privileges. This can result in unauthorized access to internal networks, interception or manipulation of sensitive data, disruption of network services, and the potential for the device to be used as a pivot point for lateral movement or launching further attacks. The vulnerability threatens confidentiality by exposing WPA-PSK configurations and other sensitive information, integrity by allowing malicious modifications to device settings or firmware, and availability by enabling denial-of-service conditions or persistent backdoors. Given the remote and unauthenticated nature of the exploit, attackers can target vulnerable devices at scale, increasing the risk to enterprises, ISPs, and home users. The lack of current known exploits in the wild provides a window for mitigation, but the public disclosure raises the urgency for proactive defense.

To mitigate CVE-2026-2877, organizations should first check for firmware updates from Tenda addressing this vulnerability and apply them promptly once available. In the absence of official patches, network administrators should restrict access to the router’s management interfaces, especially the /goform/WifiExtraSet endpoint, by implementing network segmentation and firewall rules that limit HTTP access to trusted sources only. Disabling remote management features or changing default credentials can reduce exposure. Monitoring network traffic for unusual HTTP requests targeting the vulnerable endpoint can help detect exploitation attempts. Employing intrusion detection and prevention systems (IDS/IPS) with signatures for this vulnerability can provide additional defense. Regularly auditing and inventorying network devices to identify vulnerable Tenda A18 routers is critical. Organizations should also consider replacing affected devices with models that have a stronger security posture if patches are delayed. Finally, educating users about the risks and encouraging timely updates will help reduce the attack surface.