CVE-2025-5607 is a critical buffer overflow vulnerability identified in the Tenda AC18 router, specifically affecting firmware version 15.03.05.05. The vulnerability resides in the function formSetPPTPUserList within the /goform/setPptpUserList endpoint. This function improperly handles the argument list, allowing an attacker to manipulate input data in a way that causes a buffer overflow condition. Buffer overflow vulnerabilities can lead to arbitrary code execution, denial of service, or system compromise. The vulnerability is remotely exploitable without user interaction and does not require prior authentication, making it particularly dangerous. The CVSS 4.0 base score is 8.7, indicating a high severity level with network attack vector, low attack complexity, no privileges required, and no user interaction needed. The impact metrics indicate high confidentiality, integrity, and availability impacts, meaning successful exploitation could lead to full system compromise. Although no public exploits are currently known to be in the wild, the vulnerability details have been disclosed publicly, increasing the risk of exploitation by threat actors. This vulnerability affects a widely used consumer and small business router model, which is often deployed in home and office environments, potentially exposing a large number of devices to attack if unpatched.

For European organizations, the impact of CVE-2025-5607 could be significant, especially for small and medium enterprises (SMEs) and home office users relying on Tenda AC18 routers for network connectivity. Exploitation could allow attackers to gain unauthorized access to internal networks, intercept or manipulate sensitive data, disrupt network availability, or pivot to other internal systems. This could lead to data breaches, operational disruptions, and potential regulatory non-compliance under GDPR if personal data is compromised. The remote and unauthenticated nature of the vulnerability increases the attack surface, particularly in environments where these routers are directly exposed to the internet or insufficiently segmented. Given the criticality and ease of exploitation, attackers could leverage this vulnerability for espionage, ransomware deployment, or as a foothold for broader attacks targeting European infrastructure and businesses.

Immediate mitigation should focus on updating the Tenda AC18 firmware to a version that addresses this vulnerability once available from the vendor. In the absence of a patch, organizations should implement network-level protections such as blocking access to the /goform/setPptpUserList endpoint via firewall rules or intrusion prevention systems. Network segmentation should be enforced to isolate vulnerable routers from critical internal resources. Monitoring network traffic for anomalous requests targeting the affected endpoint can help detect exploitation attempts. Disabling PPTP VPN functionality if not required can reduce the attack surface. Additionally, organizations should conduct asset inventories to identify all Tenda AC18 devices and prioritize remediation. Employing network access controls and ensuring routers are not directly exposed to the internet without protective measures will further reduce risk.