CVE-2026-2905 is a stack-based buffer overflow vulnerability identified in the Tenda HG9 router firmware version 300001138. The flaw exists in the Wireless Configuration Endpoint, specifically within the /boaform/formWlanSetup file, where the 'ssid' parameter is improperly validated or sanitized. When an attacker sends a specially crafted request manipulating the 'ssid' argument, it causes a stack buffer overflow, enabling overwriting of adjacent memory on the stack. This can lead to arbitrary code execution with the privileges of the affected process, which typically runs with elevated permissions on the device. The vulnerability is remotely exploitable without requiring user interaction or prior authentication, making it highly dangerous. The CVSS 4.0 vector indicates network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:L), no user interaction (UI:N), and high impact on confidentiality, integrity, and availability (VC:H/VI:H/VA:H). While no confirmed exploits are reported in the wild, publicly available proof-of-concept exploits increase the likelihood of active exploitation attempts. The vulnerability affects a widely deployed consumer and small business router model, which is often used in home and enterprise edge networks. Successful exploitation could allow attackers to gain persistent control over the device, intercept or manipulate network traffic, or pivot into internal networks.

The impact of CVE-2026-2905 is significant for organizations and individuals using Tenda HG9 routers. Exploitation can lead to full compromise of the device, allowing attackers to execute arbitrary code remotely. This jeopardizes the confidentiality of network traffic, potentially exposing sensitive data. Integrity is compromised as attackers could alter router configurations or inject malicious payloads into network communications. Availability may be disrupted by causing device crashes or denial-of-service conditions. For organizations, this could mean loss of network perimeter security, unauthorized access to internal resources, and potential lateral movement within corporate networks. Given the router’s role as a gateway device, the vulnerability could serve as a beachhead for broader cyberattacks. The ease of exploitation without authentication or user interaction raises the threat level, especially in environments where these routers are deployed without timely firmware updates or compensating controls.

To mitigate CVE-2026-2905, organizations should immediately check for firmware updates from Tenda addressing this vulnerability and apply them as a priority. If patches are not yet available, network administrators should restrict access to the router’s management interfaces by implementing network segmentation and firewall rules that limit inbound connections to trusted sources only. Disabling remote management features or changing default management ports can reduce exposure. Monitoring network traffic for unusual requests targeting /boaform/formWlanSetup or anomalous SSID parameter values may help detect exploitation attempts. Employing intrusion detection/prevention systems with signatures for this vulnerability can provide additional protection. For critical environments, consider replacing affected devices with models from vendors with stronger security track records. Regularly auditing router configurations and enforcing strong administrative credentials will also help reduce risk.