CVE-2026-4902 is a stack-based buffer overflow vulnerability identified in the Tenda AC5 router firmware version 15.03.06.47. The flaw resides in the fromAddressNat function, which processes POST requests at the /goform/addressNat endpoint. Specifically, the vulnerability arises from improper handling of the 'page' argument, allowing an attacker to overflow a stack buffer. This overflow can corrupt the stack, potentially overwriting the return address or other control data, enabling remote code execution. The vulnerability requires no authentication or user interaction, making it remotely exploitable over the network. The CVSS v4.0 score of 8.7 reflects the high impact on confidentiality, integrity, and availability, with low attack complexity and no privileges required. Although no exploits have been observed in the wild yet, a public exploit is available, increasing the likelihood of active exploitation. The lack of available patches at the time of disclosure means affected users must rely on mitigation strategies until an official update is released. This vulnerability poses a significant risk to network security, as compromised routers can be used to intercept, manipulate, or disrupt network traffic, or serve as footholds for further attacks within organizational networks.

The impact of CVE-2026-4902 is substantial for organizations using Tenda AC5 routers. Successful exploitation can lead to full device compromise, allowing attackers to execute arbitrary code with elevated privileges. This can result in unauthorized access to internal networks, interception and manipulation of network traffic, disruption of network services, and potential lateral movement to other critical systems. The vulnerability threatens the confidentiality of sensitive data passing through the router, the integrity of network configurations and communications, and the availability of network services. Given the router's role as a network gateway, exploitation could facilitate large-scale attacks such as man-in-the-middle, denial of service, or persistent backdoors. Organizations in sectors relying heavily on network availability and security, such as finance, healthcare, and critical infrastructure, face heightened risks. The remote and unauthenticated nature of the exploit increases the attack surface and urgency for mitigation.

To mitigate CVE-2026-4902, organizations should immediately isolate affected Tenda AC5 routers from untrusted networks to reduce exposure. Network administrators should implement strict ingress filtering and firewall rules to restrict access to the /goform/addressNat endpoint, especially blocking POST requests from untrusted sources. Employ network segmentation to limit the impact of potential compromises. Monitor network traffic for unusual POST requests targeting the vulnerable endpoint and signs of exploitation attempts. Since no official patches are currently available, consider temporary replacement or upgrade to alternative hardware with secure firmware. Engage with Tenda support channels to obtain firmware updates or security advisories. Additionally, implement intrusion detection/prevention systems (IDS/IPS) with signatures targeting this vulnerability and related exploit patterns. Regularly audit router configurations and logs for anomalies. Educate staff about the risks and signs of router compromise to enable rapid response.