CVE-2025-7531 is a critical stack-based buffer overflow vulnerability found in the Tenda FH1202 router, specifically in firmware version 1.2.0.14(408). The flaw exists in the function fromPptpUserSetting within the /goform/PPTPUserSetting endpoint. The vulnerability arises from improper handling of the 'delno' argument, which can be manipulated by an attacker to overflow the stack buffer. This overflow can lead to arbitrary code execution or cause the device to crash, resulting in denial of service. The vulnerability is remotely exploitable over the network without requiring user interaction or prior authentication, making it highly dangerous. The CVSS 4.0 base score is 8.7 (high severity), reflecting the ease of exploitation (network attack vector, low complexity), no privileges required, and no user interaction needed. The impact on confidentiality, integrity, and availability is high, as the attacker can potentially execute arbitrary code with system-level privileges, compromising the device and the network it serves. Although no public exploits are currently known in the wild, the vulnerability details have been disclosed publicly, increasing the risk of exploitation by threat actors. The Tenda FH1202 is a consumer and small office/home office (SOHO) router, often deployed in residential and small business environments. The vulnerability affects the router's PPTP user setting management interface, which is typically exposed on the device's web management interface or possibly through network services, increasing the attack surface.

For European organizations, especially small businesses and residential users relying on Tenda FH1202 routers, this vulnerability poses a significant risk. Successful exploitation could lead to complete compromise of the affected router, allowing attackers to intercept, manipulate, or redirect network traffic, potentially leading to data breaches, espionage, or lateral movement within corporate networks. The disruption of network availability due to device crashes or reboots can impact business continuity. Given the router's role as a network gateway, attackers could also use compromised devices as footholds for launching further attacks against internal systems or as part of botnets for broader campaigns. The high severity and remote exploitability without authentication make this a critical concern for organizations that have not yet updated or mitigated the vulnerability. Additionally, the lack of an official patch at the time of disclosure increases exposure duration.

1. Immediate mitigation should include isolating affected Tenda FH1202 devices from critical network segments to limit potential impact. 2. Disable PPTP VPN functionality or the /goform/PPTPUserSetting interface if not required, reducing the attack surface. 3. Implement network-level access controls to restrict management interface access to trusted IP addresses only. 4. Monitor network traffic for unusual activity or signs of exploitation attempts targeting the delno parameter or the PPTP user settings endpoint. 5. Regularly check for firmware updates from Tenda and apply patches promptly once available. 6. Consider replacing affected devices with routers from vendors with a stronger security track record if patches are delayed. 7. Employ intrusion detection/prevention systems (IDS/IPS) with signatures targeting this vulnerability once available. 8. Educate users and administrators about the risks of using outdated router firmware and the importance of secure configuration.