CVE-2025-5794 is a critical buffer overflow vulnerability identified in the Tenda AC5 router firmware version 15.03.06.47. The vulnerability exists in the function formSetPPTPUserList within the /goform/setPptpUserList endpoint. This function improperly handles the argument list, allowing an attacker to overflow a buffer by sending crafted input. The vulnerability can be exploited remotely without requiring user interaction or prior authentication, as indicated by the CVSS vector (AV:N/AC:L/AT:N/UI:N/PR:L). The buffer overflow can lead to severe consequences including arbitrary code execution, denial of service, or system compromise due to the high impact on confidentiality, integrity, and availability (VC:H/VI:H/VA:H). Although no public exploits are currently known to be actively used in the wild, the exploit code has been disclosed publicly, increasing the risk of exploitation. The vulnerability affects a widely used consumer-grade router model, which is often deployed in home and small office environments. The lack of available patches at the time of disclosure further exacerbates the risk. Given the critical nature of the flaw and the ease of remote exploitation, this vulnerability represents a significant threat to affected networks.

For European organizations, the impact of this vulnerability can be substantial, especially for small and medium enterprises (SMEs) and home office users relying on Tenda AC5 routers for network connectivity. Successful exploitation could allow attackers to gain unauthorized access to internal networks, intercept or manipulate sensitive data, and disrupt network availability. This could lead to data breaches, loss of business continuity, and potential regulatory non-compliance under GDPR if personal data is compromised. Additionally, compromised routers could be leveraged as entry points for lateral movement within corporate networks or as part of botnets for broader attacks. The remote and unauthenticated nature of the exploit increases the attack surface, making it easier for threat actors to target vulnerable devices across Europe. The absence of patches at the time of disclosure means organizations must rely on interim mitigations, increasing operational risk.

1. Immediate network segmentation: Isolate Tenda AC5 routers from critical infrastructure and sensitive data networks to limit potential lateral movement in case of compromise. 2. Disable PPTP VPN functionality if not in use, as the vulnerability is located in the PPTP user list management function. 3. Implement strict firewall rules to restrict inbound access to router management interfaces, especially the /goform/setPptpUserList endpoint, limiting exposure to untrusted networks. 4. Monitor network traffic for unusual patterns or attempts to exploit the /goform/setPptpUserList endpoint, using IDS/IPS solutions with custom signatures if necessary. 5. Engage with Tenda support channels to obtain firmware updates or patches as soon as they become available and plan for prompt deployment. 6. Consider replacing affected routers with alternative models from vendors with a stronger security track record if patching is delayed. 7. Educate users and administrators about the risks and signs of exploitation to enable rapid detection and response.