CVE-2025-10838 is a high-severity buffer overflow vulnerability affecting the Tenda AC21 router, specifically version 16.03.08.16. The vulnerability resides in the function sub_45BB10 within the /goform/WifiExtraSet file. It is triggered by manipulating the 'wpapsk_crypto' argument, which leads to a buffer overflow condition. This flaw can be exploited remotely without requiring user interaction or prior authentication, making it particularly dangerous. The vulnerability allows an attacker to potentially execute arbitrary code with elevated privileges, compromising the confidentiality, integrity, and availability of the affected device. The CVSS 4.0 base score is 8.7, reflecting the ease of exploitation (network vector, low attack complexity), no required privileges or user interaction, and a high impact on all security properties. Although no known exploits are currently observed in the wild, a public exploit is available, increasing the risk of exploitation. The Tenda AC21 is a consumer and small office/home office (SOHO) router, commonly used to provide wireless connectivity. Exploitation could lead to full device compromise, enabling attackers to intercept or manipulate network traffic, launch further attacks within the network, or disrupt network services.

For European organizations, especially small and medium enterprises (SMEs) and home office users relying on Tenda AC21 routers, this vulnerability poses a significant risk. Successful exploitation could lead to unauthorized access to internal networks, data interception, and lateral movement to more critical infrastructure. Confidential business communications and sensitive data could be exposed or altered. The availability of network services might be disrupted, impacting business operations. Given the remote and unauthenticated nature of the exploit, attackers could leverage this vulnerability as an entry point for broader cyberattacks, including ransomware or espionage campaigns. The impact is particularly critical for organizations handling sensitive personal data under GDPR, as breaches could result in regulatory penalties and reputational damage.

To mitigate this vulnerability, organizations should immediately verify if their Tenda AC21 routers are running the affected firmware version 16.03.08.16. Since no official patch links are currently available, users should monitor Tenda's official channels for firmware updates addressing CVE-2025-10838 and apply them promptly once released. In the interim, it is advisable to restrict remote management access to the router by disabling WAN-side administration or limiting access to trusted IP addresses only. Network segmentation should be employed to isolate vulnerable devices from critical systems. Deploying network intrusion detection/prevention systems (IDS/IPS) with signatures for this exploit can help detect and block attack attempts. Additionally, replacing vulnerable devices with models from vendors with timely security support should be considered for long-term risk reduction. Regularly auditing network devices and maintaining an asset inventory will aid in rapid identification and response to such vulnerabilities.