CVE-2025-11327 is a stack-based buffer overflow vulnerability identified in the Tenda AC18 router firmware version 15.03.05.19(6318). The vulnerability resides in the /goform/SetUpnpCfg endpoint, specifically in the handling of the upnpEn parameter. Improper input validation or bounds checking allows an attacker to send a specially crafted request that overflows the stack buffer, potentially overwriting the return address or other control data. This can lead to arbitrary code execution on the device with elevated privileges, as the router firmware typically runs with high system rights. The vulnerability can be exploited remotely over the network without requiring authentication or user interaction, making it highly dangerous. The CVSS v4.0 base score is 8.7, reflecting the high impact on confidentiality, integrity, and availability, combined with the low attack complexity and no required privileges. Although no exploits are currently reported in the wild, the public disclosure of the vulnerability increases the risk of exploitation by threat actors. The Tenda AC18 is a widely used consumer and small business router, often deployed in home and small office environments, which may have less stringent network protections and more exposure to the internet. Attackers exploiting this vulnerability could gain control over the router, intercept or manipulate network traffic, launch further attacks on internal networks, or disrupt network availability.

For European organizations, the impact of CVE-2025-11327 could be significant, especially for small and medium enterprises (SMEs) and home office users relying on Tenda AC18 routers. Successful exploitation can lead to full compromise of the router, allowing attackers to intercept sensitive communications, manipulate network traffic, or pivot to internal systems. This threatens confidentiality, integrity, and availability of organizational data and services. Disruption of network connectivity could impact business operations, while unauthorized access could facilitate further attacks such as data exfiltration or ransomware deployment. Given the router’s role as a network gateway, compromise could undermine perimeter defenses and expose internal assets. The risk is heightened in environments where remote management interfaces are exposed to the internet without adequate protections. Additionally, the lack of current patches means organizations must rely on network-level mitigations until vendor updates are released. The vulnerability also poses risks to critical infrastructure sectors that may use such routers in less monitored environments.

1. Immediately restrict remote access to the router’s management interfaces, especially the /goform/SetUpnpCfg endpoint, by disabling remote administration or limiting access via firewall rules to trusted IP addresses. 2. Monitor network traffic for unusual or malformed requests targeting the /goform/SetUpnpCfg endpoint or other management URLs. 3. Implement network segmentation to isolate vulnerable routers from critical internal systems, reducing potential lateral movement. 4. Disable UPnP functionality if not required, as it is related to the vulnerable parameter, to reduce attack surface. 5. Regularly check for firmware updates from Tenda and apply patches promptly once available. 6. Employ intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics capable of detecting exploitation attempts targeting this vulnerability. 7. Educate users and administrators about the risks of exposing router management interfaces to the internet and enforce strong network security policies. 8. Consider replacing vulnerable devices with models from vendors with stronger security track records if timely patches are not forthcoming.