CVE-2026-2930 is a stack-based buffer overflow vulnerability found in the Tenda A18 router firmware version 15.13.07.13. The flaw exists in the webCgiGetUploadFile function within the /cgi-bin/UploadCfg endpoint of the HTTP daemon service. This function improperly handles the boundary of an input argument, allowing an attacker to overflow the stack buffer. Exploiting this vulnerability remotely can lead to memory corruption, which may enable arbitrary code execution or cause the device to crash, resulting in denial of service. The vulnerability does not require authentication or user interaction, increasing its risk profile. The exploit code is publicly available, which could facilitate attacks by less skilled adversaries. However, no active exploitation has been reported to date. The vulnerability has a CVSS 4.0 score of 5.3, reflecting medium severity due to limited impact on confidentiality, integrity, and availability, and the requirement for some privileges (PR:L) but no user interaction. The affected product, Tenda A18, is a consumer-grade wireless router commonly used in home and small office environments. The lack of an official patch at the time of disclosure necessitates interim mitigations to reduce exposure.

The primary impact of CVE-2026-2930 is the potential for remote attackers to execute arbitrary code or cause denial of service on affected Tenda A18 routers. Successful exploitation could allow attackers to gain control over the device, manipulate network traffic, intercept sensitive data, or disrupt network connectivity. This poses risks to the confidentiality, integrity, and availability of networks relying on these routers. For organizations, compromised routers could serve as entry points for lateral movement or be leveraged in botnets for broader attacks. Given the router's typical deployment in home and small office environments, the impact is more pronounced for small businesses and residential users who may lack robust network defenses. The availability of a public exploit increases the likelihood of opportunistic attacks, especially if devices remain unpatched. However, the medium severity score and requirement for some privileges reduce the risk compared to more critical vulnerabilities.

Organizations and users should monitor Tenda's official channels for firmware updates addressing this vulnerability and apply patches promptly once released. Until a patch is available, network administrators should restrict access to the router's management interface, especially the /cgi-bin/UploadCfg endpoint, by implementing firewall rules or access control lists that limit connections to trusted IP addresses. Disabling remote management features on the router can further reduce exposure. Network segmentation should be employed to isolate vulnerable devices from critical infrastructure. Intrusion detection systems (IDS) and intrusion prevention systems (IPS) should be configured to detect and block exploit attempts targeting this vulnerability. Regularly auditing router configurations and monitoring network traffic for anomalies can help identify exploitation attempts. Users should also consider replacing outdated or unsupported devices with models that receive timely security updates.