CVE-2025-14656 is a buffer overflow vulnerability identified in the Tenda AC20 router firmware version 16.03.08.12. The vulnerability resides in the HTTP daemon (httpd) component, specifically in the handling of the /goform/openSchedWifi endpoint. Attackers can manipulate the schedStartTime and schedEndTime parameters to overflow a buffer, potentially overwriting adjacent memory. This flaw can be exploited remotely without requiring authentication or user interaction, making it highly accessible to attackers. The buffer overflow could lead to remote code execution, allowing attackers to execute arbitrary code with elevated privileges on the device, or cause denial of service by crashing the router. The vulnerability has a CVSS 4.0 base score of 8.7, indicating high severity due to its network attack vector, low complexity, no required privileges or user interaction, and high impact on confidentiality, integrity, and availability. Although no active exploitation has been reported in the wild, a public exploit is available, increasing the likelihood of future attacks. The affected product, Tenda AC20, is a widely used consumer and small business router, which increases the scope of potential impact. The lack of an official patch link suggests that a firmware update may not yet be available, emphasizing the need for interim mitigations. This vulnerability is critical for organizations relying on Tenda AC20 devices for network connectivity, as exploitation could compromise internal networks or disrupt services.

The impact of CVE-2025-14656 is significant for organizations using Tenda AC20 routers, particularly in environments where these devices serve as primary network gateways. Successful exploitation can lead to remote code execution, allowing attackers to gain control over the router, intercept or manipulate network traffic, and potentially pivot to internal systems. This compromises confidentiality by exposing sensitive data, integrity by allowing unauthorized changes to network configurations or traffic, and availability by causing device crashes or network outages. The vulnerability's remote, unauthenticated exploitability increases the attack surface, especially for devices exposed to the internet or untrusted networks. Organizations could face operational disruptions, data breaches, and increased risk of lateral movement by threat actors. The availability of a public exploit further elevates the risk of widespread attacks, including automated scanning and exploitation campaigns. Critical infrastructure, small and medium enterprises, and home users relying on Tenda AC20 devices are all at risk, with potential cascading effects on business continuity and security posture.

1. Immediately restrict remote access to the router's management interface by disabling WAN-side administration or limiting access via firewall rules and VPNs. 2. Monitor network traffic for unusual activity targeting the /goform/openSchedWifi endpoint and implement intrusion detection/prevention systems (IDS/IPS) with signatures for this exploit. 3. Apply firmware updates from Tenda as soon as they are released addressing this vulnerability. If no official patch is available, consider temporary mitigation by disabling or restricting the vulnerable service if possible. 4. Segment networks to isolate vulnerable devices from critical infrastructure and sensitive data to limit potential lateral movement. 5. Conduct regular vulnerability scans and penetration tests to identify exposed Tenda AC20 devices and verify mitigation effectiveness. 6. Educate users and administrators on the risks of exposing router management interfaces to untrusted networks. 7. Maintain up-to-date asset inventories to quickly identify and remediate affected devices. 8. Consider deploying network-level protections such as web application firewalls (WAFs) or network access control (NAC) to block exploit attempts.