CVE-2026-2886 identifies a critical stack-based buffer overflow vulnerability in the Tenda A21 router firmware version 1.0.0.0. The vulnerability resides in the set_device_name function, which processes the devName parameter submitted via the /goform/SetOnlineDevName HTTP endpoint. Improper validation or bounds checking of this input allows an attacker to overflow the stack buffer, corrupting adjacent memory. This can lead to arbitrary code execution, enabling full control over the affected device, or cause denial of service through crashes. The attack vector is remote network access, requiring no authentication or user interaction, making exploitation straightforward. The CVSS 4.0 score of 8.7 reflects the high impact on confidentiality, integrity, and availability, combined with low attack complexity and no privileges required. While no active exploitation in the wild has been reported, the availability of a public exploit significantly raises the threat level. The vulnerability affects only the initial firmware version 1.0.0.0 of the Tenda A21, a consumer-grade router commonly used in home and small office environments. The lack of an official patch or update at the time of disclosure increases exposure risk. Attackers could leverage this flaw to gain persistent access, intercept or manipulate network traffic, or pivot to internal networks.

The impact of CVE-2026-2886 is substantial for organizations and individuals using the Tenda A21 router with firmware version 1.0.0.0. Successful exploitation can result in complete compromise of the router, allowing attackers to execute arbitrary code with system-level privileges. This can lead to interception of sensitive data, network traffic manipulation, insertion of malicious payloads, or disruption of network availability. For enterprises relying on these devices in branch offices or home offices, this vulnerability could serve as an entry point for lateral movement into corporate networks. The absence of authentication and user interaction requirements lowers the barrier for attackers, increasing the likelihood of exploitation. The public availability of an exploit further elevates the risk of widespread attacks. Additionally, compromised routers can be recruited into botnets or used to launch further attacks, amplifying the threat beyond the initial target. The vulnerability's impact extends to confidentiality, integrity, and availability, making it a critical concern for network security.

To mitigate CVE-2026-2886, organizations should immediately restrict external access to the Tenda A21 router's management interfaces, especially the /goform/SetOnlineDevName endpoint, by implementing network segmentation and firewall rules that block untrusted inbound traffic. Disable remote management features if not required. Monitor network traffic for unusual requests targeting the vulnerable endpoint and deploy intrusion detection/prevention systems with signatures for this exploit. Since no official patch is currently available, consider upgrading to a newer firmware version if released by Tenda or replacing the affected device with a more secure model. Employ network-level protections such as VPNs for remote access to reduce exposure. Regularly audit and inventory network devices to identify vulnerable routers. Educate users about the risks of exposing router management interfaces to the internet. Finally, maintain backups and incident response plans to quickly recover from potential compromises.