CVE-2025-5852 is a critical buffer overflow vulnerability identified in the Tenda AC6 router firmware version 15.03.05.16. The flaw exists in the function formSetPPTPUserList within the /goform/setPptpUserList endpoint. Specifically, the vulnerability arises from improper handling and validation of the argument list passed to this function, which allows an attacker to overflow a buffer. This type of vulnerability can lead to arbitrary code execution, denial of service, or system compromise. 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 CVSS score of 8.7 (high severity) reflects the significant risk posed by this flaw. Although no known exploits are currently observed in the wild, the exploit code has been publicly disclosed, increasing the likelihood of exploitation attempts. The vulnerability impacts the confidentiality, integrity, and availability of the affected device, as successful exploitation can allow attackers to execute arbitrary commands with elevated privileges, potentially taking full control of the router. Given that the Tenda AC6 is a widely used consumer and small office/home office (SOHO) router, exploitation could also facilitate lateral movement within networks or interception of network traffic.

For European organizations, the exploitation of CVE-2025-5852 could have severe consequences. Many small and medium enterprises (SMEs) and home offices rely on consumer-grade routers like the Tenda AC6 for internet connectivity. A compromised router could lead to interception of sensitive communications, unauthorized network access, and disruption of business operations. The vulnerability's remote exploitability without authentication means attackers can target exposed devices over the internet or local networks. This could result in data breaches, espionage, or use of compromised routers as pivot points for further attacks. Critical infrastructure or organizations with remote workers using vulnerable routers may face increased risk. Additionally, the public disclosure of exploit code raises the threat level, as less skilled attackers can attempt exploitation. The impact extends beyond confidentiality to integrity and availability, potentially causing network outages or manipulation of traffic flows.

To mitigate CVE-2025-5852 effectively, European organizations and users should: 1) Immediately check for firmware updates from Tenda addressing this vulnerability and apply patches as soon as they become available. 2) If patches are not yet released, consider temporarily disabling the PPTP user list configuration interface or restricting access to the /goform/setPptpUserList endpoint via firewall rules or network segmentation to limit exposure. 3) Employ network-level protections such as intrusion detection/prevention systems (IDS/IPS) configured to detect anomalous requests targeting this endpoint. 4) Replace vulnerable Tenda AC6 devices with more secure alternatives if patching is delayed or unsupported. 5) Monitor network traffic for signs of exploitation attempts, including unusual outbound connections or command execution patterns. 6) Educate users about the risks of using outdated router firmware and encourage regular updates. 7) For organizations, enforce strict network access controls and consider VPN usage to reduce exposure of vulnerable devices to the internet. These steps go beyond generic advice by focusing on immediate containment, proactive monitoring, and device lifecycle management.