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 within the /goform/openSchedWifi endpoint. This endpoint processes scheduling parameters for Wi-Fi operation, including schedStartTime and schedEndTime. Improper input validation or bounds checking on these parameters allows an attacker to craft malicious HTTP requests that overflow the buffer allocated for these inputs. This overflow can corrupt adjacent memory, potentially enabling remote code execution with elevated privileges on the device. The attack vector is network-based (AV:N), requiring no authentication (AT:N) or user interaction (UI:N), and has low attack complexity (AC:L). The vulnerability affects the confidentiality, integrity, and availability of the device, as an attacker could execute arbitrary code, disrupt network services, or intercept sensitive data. Although no active exploitation has been reported, the availability of a public exploit increases the urgency for remediation. The vulnerability does not require physical access or user involvement, making it highly exploitable in exposed network environments. The lack of a vendor patch at the time of disclosure necessitates interim mitigations to reduce exposure. This vulnerability is critical for environments relying on Tenda AC20 routers, including home networks, small businesses, and ISPs using these devices as customer premises equipment (CPE).

For European organizations, exploitation of CVE-2025-14656 could lead to severe consequences including unauthorized remote code execution on network routers, resulting in full compromise of the device. This can enable attackers to intercept or manipulate network traffic, disrupt connectivity, or use the compromised router as a foothold for lateral movement into internal networks. Confidentiality of sensitive communications could be breached, integrity of network configurations compromised, and availability of network services disrupted. Organizations relying on Tenda AC20 routers for critical infrastructure or customer connectivity face increased risk of operational downtime and data breaches. The public availability of an exploit increases the likelihood of targeted attacks or opportunistic scanning by threat actors. Given the router’s role at the network edge, successful exploitation could undermine perimeter defenses and expose internal systems to further compromise. The impact is particularly significant for sectors with stringent data protection requirements under GDPR, as breaches could result in regulatory penalties and reputational damage.

1. Immediately restrict external network access to the management interface of Tenda AC20 routers, especially blocking HTTP access to the /goform/openSchedWifi endpoint at the firewall or router level. 2. Monitor network traffic for unusual or malformed HTTP requests targeting the vulnerable endpoint to detect potential exploitation attempts. 3. Deploy network intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics capable of identifying buffer overflow attempts against this vulnerability. 4. Isolate vulnerable devices on segmented networks to limit potential lateral movement if compromised. 5. Engage with Tenda support channels to obtain and apply official firmware updates as soon as they become available. 6. In the absence of patches, consider temporary replacement of vulnerable devices with alternative hardware or firmware versions not affected by this issue. 7. Educate network administrators about the vulnerability and ensure strict access controls and strong authentication mechanisms are in place for device management. 8. Conduct regular vulnerability scans and penetration tests focusing on network edge devices to identify and remediate similar issues proactively.