CVE-2025-5798 is a critical stack-based buffer overflow vulnerability identified in the Tenda AC8 router firmware version 16.03.34.09. The vulnerability resides in the function fromSetSysTime within the /goform/SetSysTimeCfg endpoint. Specifically, the issue arises from improper handling and validation of the 'timeType' argument, which an attacker can manipulate to overflow the stack buffer. This overflow can lead to arbitrary code execution or cause the device to crash, resulting in denial of service. The vulnerability is remotely exploitable without requiring user interaction or prior authentication, as indicated by the CVSS vector (AV:N/AC:L/AT:N/UI:N/PR:L). The exploit has been publicly disclosed, increasing the risk of exploitation, although no known active exploits in the wild have been reported yet. The CVSS 4.0 base score of 8.7 classifies this vulnerability as high severity, reflecting its potential to compromise confidentiality, integrity, and availability of affected devices. Given that Tenda AC8 routers are commonly used in home and small office environments, exploitation could allow attackers to gain control over network traffic, intercept sensitive data, or pivot into internal networks. The lack of available patches at the time of disclosure further elevates the risk for users of this firmware version.

For European organizations, the impact of this vulnerability can be significant, especially for small and medium enterprises (SMEs) and home offices relying on Tenda AC8 routers for internet connectivity. Successful exploitation could lead to unauthorized remote code execution, enabling attackers to intercept or manipulate network traffic, deploy malware, or establish persistent footholds within internal networks. This could result in data breaches, disruption of business operations, and compromise of sensitive information. Additionally, the vulnerability could be leveraged to launch distributed denial-of-service (DDoS) attacks using compromised devices. Given the critical nature of the flaw and the ease of remote exploitation without authentication, organizations with inadequate network segmentation or outdated firmware are particularly at risk. The public disclosure of the exploit code increases the likelihood of opportunistic attacks targeting vulnerable devices across Europe.

Organizations should immediately assess their network infrastructure to identify any Tenda AC8 routers running firmware version 16.03.34.09. Since no official patches are currently available, mitigation should focus on reducing exposure: 1) Restrict remote access to router management interfaces by disabling WAN-side administration or limiting access via firewall rules to trusted IP addresses. 2) Implement network segmentation to isolate vulnerable devices from critical systems and sensitive data. 3) Monitor network traffic for unusual activity indicative of exploitation attempts, such as unexpected outbound connections or anomalous traffic patterns. 4) If possible, downgrade or upgrade to a firmware version not affected by this vulnerability once a patch is released. 5) Educate users about the risks and encourage regular firmware updates. 6) Employ intrusion detection/prevention systems (IDS/IPS) with signatures targeting this vulnerability once available. 7) Consider replacing vulnerable devices with models from vendors with timely security support if patching is not feasible.