CVE-2025-28220 is a high-severity buffer overflow vulnerability identified in the Tenda W6_S device firmware version 1.0.0.4_510. The vulnerability exists within the setcfm function, which processes input parameters received via HTTP POST requests. Specifically, the parameter funcpara1 can be manipulated by a remote attacker to trigger a buffer overflow condition. This overflow can cause the embedded web server on the device to crash, resulting in a denial of service (DoS) condition. The vulnerability does not require any authentication or user interaction, and it can be exploited remotely over the network, as indicated by the CVSS vector (AV:N/AC:L/PR:N/UI:N). The vulnerability is classified under CWE-120, which corresponds to classic buffer overflow issues where improper bounds checking allows memory corruption. Although no known exploits are currently reported in the wild, the ease of exploitation combined with the lack of authentication requirements makes this a significant threat to affected devices. The impact is limited to availability, as there is no indication of confidentiality or integrity compromise. However, the crash of the web server could disrupt device management and network operations dependent on the device. No patches or vendor advisories have been linked yet, indicating that mitigation may rely on network-level controls or device replacement until a firmware update is released.

For European organizations, the primary impact of this vulnerability is the potential disruption of network infrastructure relying on Tenda W6_S devices. These devices are typically used as wireless access points or routers in small to medium-sized enterprise environments or home offices. An attacker exploiting this vulnerability could cause repeated crashes of the device's web management interface, leading to denial of service and loss of remote management capabilities. This could hinder network administration and incident response efforts. While the vulnerability does not directly compromise data confidentiality or integrity, the resulting downtime could affect business continuity, especially in environments where these devices serve as critical network access points. Additionally, if attackers use this vulnerability as part of a broader attack chain, it could facilitate lateral movement or network segmentation bypass by disabling security controls embedded in the device. The lack of known exploits in the wild reduces immediate risk but does not eliminate the threat, especially as proof-of-concept exploits could emerge. Organizations with remote or distributed workforces relying on these devices may experience increased exposure due to the remote exploitability of the flaw.

Given the absence of an official patch or firmware update, European organizations should implement the following specific mitigations: 1) Network Segmentation: Isolate Tenda W6_S devices on dedicated management VLANs with restricted access to minimize exposure to untrusted networks. 2) Access Control: Restrict inbound HTTP POST requests to the device's management interface using firewall rules or access control lists (ACLs), allowing only trusted IP addresses or management stations. 3) Monitoring and Detection: Deploy network intrusion detection systems (NIDS) to monitor for anomalous POST requests targeting the setcfm function or unusual traffic patterns indicative of exploitation attempts. 4) Device Replacement: Where feasible, replace vulnerable Tenda W6_S devices with models from vendors providing timely security updates and robust vulnerability management. 5) Vendor Engagement: Engage with Tenda support channels to obtain information on planned patches or firmware updates and apply them promptly once available. 6) Incident Response Preparedness: Prepare for potential denial of service incidents by establishing procedures for rapid device reboot or replacement to minimize downtime. 7) Disable Unused Services: If possible, disable the web management interface or restrict it to local access only to reduce the attack surface. These measures go beyond generic advice by focusing on network-level controls and operational readiness tailored to the specific characteristics of this vulnerability.