CVE-2025-28221 is a buffer overflow vulnerability identified in the Tenda W6_S device firmware version 1.0.0.4_510. The flaw exists in the set_local_time function, which processes a 'time' parameter received via a POST request to the device's web server interface. Due to improper bounds checking or input validation in this function, an attacker can craft a specially formed POST request that causes a buffer overflow. This overflow can lead to a crash of the embedded web server, resulting in a denial of service (DoS) condition. The vulnerability is remotely exploitable over the network without requiring any authentication or user interaction, making it accessible to unauthenticated attackers. The CVSS v3.1 base score is 7.5, indicating a high severity level primarily due to the ease of remote exploitation and the impact on availability. However, the vulnerability does not affect confidentiality or integrity directly, as it does not allow code execution or data leakage based on the current information. No patches or fixes have been published yet, and there are no known exploits in the wild at this time. The vulnerability is classified under CWE-120, which relates to classic buffer overflow issues, a common and well-understood software weakness. The affected product is a Tenda W6_S device, which is a consumer or small office wireless router or access point, though the exact product details and affected versions beyond the stated firmware are not fully specified.

For European organizations, the primary impact of this vulnerability is the potential disruption of network availability caused by the forced crash of the Tenda W6_S device's web server. This could lead to temporary loss of management access to the device, impacting network administration and potentially causing network outages if the device is critical in the network topology. Since the vulnerability does not allow remote code execution or data compromise, the risk to confidentiality and integrity is low. However, denial of service on network infrastructure devices can have cascading effects, especially in environments relying on these devices for connectivity or security enforcement. Small and medium enterprises (SMEs) or branch offices using Tenda W6_S devices may be particularly vulnerable if they lack redundant network paths or rapid device replacement capabilities. The lack of authentication requirement and remote exploitability increase the risk of automated scanning and exploitation attempts once public awareness grows. Although no exploits are currently known in the wild, the high CVSS score and ease of exploitation suggest that attackers may develop exploits in the future, increasing risk over time.

Given the absence of an official patch, European organizations should implement several practical mitigations: 1) Network Segmentation: Isolate Tenda W6_S devices from untrusted networks and restrict management interface access to trusted administrators only, preferably via VPN or secure management VLANs. 2) Access Controls: Employ firewall rules to limit inbound POST requests to the device’s web server from only authorized IP addresses to reduce exposure. 3) Monitoring and Detection: Deploy network monitoring to detect unusual POST requests or repeated crashes of the device’s web server, which may indicate exploitation attempts. 4) Device Replacement or Firmware Updates: Engage with Tenda support channels to obtain firmware updates or consider replacing vulnerable devices with models from vendors with active security support. 5) Incident Response Preparedness: Prepare for potential denial of service incidents by maintaining spare devices and documented recovery procedures to minimize downtime. 6) Disable Unused Services: If possible, disable the web management interface or restrict it to local access only to reduce the attack surface. 7) Vendor Communication: Maintain communication with Tenda for timely updates or patches and subscribe to vulnerability advisories related to this product.