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 the wpapsk_crypto5g parameter in the /goform/WifiExtraSet HTTP endpoint, which is part of the Httpd Service component. The strcpy function is used insecurely to copy this parameter without adequate bounds checking, leading to a buffer overflow on the stack. This overflow can corrupt adjacent memory, potentially allowing an attacker to execute arbitrary code remotely. The attack vector is network-based, requiring no authentication or user interaction, making it highly accessible to remote attackers. The CVSS v4.0 score of 8.7 reflects the critical nature of the vulnerability, with high impact on confidentiality, integrity, and availability. Although no exploits have been observed in the wild yet, the public disclosure of the exploit code increases the likelihood of exploitation attempts. The vulnerability affects only the specified firmware version, and no patches have been linked yet, indicating that mitigation relies on vendor updates or workarounds.

The exploitation of this vulnerability can lead to full compromise of affected Tenda A18 routers. Attackers could execute arbitrary code with elevated privileges, potentially gaining control over the device. This can result in interception or manipulation of network traffic, disruption of network services, or use of the compromised router as a foothold for further attacks within the network. The confidentiality, integrity, and availability of network communications are at significant risk. Organizations relying on these routers for critical network infrastructure or internet access may face operational disruptions, data breaches, or lateral movement by attackers. The remote and unauthenticated nature of the exploit increases the risk of widespread attacks, especially in environments where these devices are exposed to untrusted networks.

Organizations should immediately inventory their network to identify any Tenda A18 devices running firmware version 15.13.07.13. Until an official patch is released, network administrators should restrict access to the management interface by implementing firewall rules that limit HTTP access to trusted internal IP addresses only. Disabling remote management features on the affected devices can reduce exposure. Monitoring network traffic for unusual requests to the /goform/WifiExtraSet endpoint may help detect exploitation attempts. If possible, upgrading to a newer firmware version that addresses this vulnerability should be prioritized once available. Additionally, network segmentation can limit the impact of a compromised device. Employing intrusion detection/prevention systems with signatures for this vulnerability can provide further defense.