CVE-2025-7805 is a critical security vulnerability identified in the Tenda FH451 router, specifically version 1.0.0.9. The flaw exists in the function fromPptpUserSetting within the /goform/PPTPUserSetting endpoint. The vulnerability arises from improper handling of the 'delno' argument, which leads to a stack-based buffer overflow condition. This type of vulnerability occurs when data exceeding the buffer's capacity is written to the stack, potentially overwriting adjacent memory and enabling arbitrary code execution or system crashes. 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, with high impact on confidentiality, integrity, and availability (VC:H/VI:H/VA:H). Although no known exploits are currently observed in the wild, the public disclosure of the exploit code increases the risk of active exploitation. The vulnerability affects only the specified firmware version 1.0.0.9 of the Tenda FH451, a consumer-grade router device. The attack vector involves sending specially crafted requests to the vulnerable endpoint, which can trigger the buffer overflow and potentially allow remote attackers to execute arbitrary code with elevated privileges, leading to full compromise of the device. Given the critical nature of routers as network gateways, exploitation could enable attackers to intercept, manipulate, or disrupt network traffic, launch further attacks on internal networks, or create persistent backdoors.

For European organizations, the exploitation of CVE-2025-7805 could have severe consequences. Many small and medium enterprises (SMEs) and even some larger organizations rely on consumer-grade routers like the Tenda FH451 for network connectivity, especially in remote or branch office environments. A successful attack could lead to complete takeover of the router, allowing attackers to intercept sensitive communications, inject malicious traffic, or pivot into internal networks. This compromises confidentiality and integrity of organizational data and can disrupt availability of critical network services. Additionally, compromised routers can be used as launchpads for further attacks such as lateral movement, data exfiltration, or participation in botnets. The lack of authentication requirement and ease of remote exploitation increase the risk of widespread attacks. Furthermore, organizations subject to strict data protection regulations such as GDPR could face compliance violations and reputational damage if breaches occur due to this vulnerability.

To mitigate the risk posed by CVE-2025-7805, European organizations should take the following specific actions: 1) Immediately identify all Tenda FH451 devices running firmware version 1.0.0.9 within their networks. 2) Check for and apply any available firmware updates or patches from Tenda addressing this vulnerability; if no official patch is available, consider upgrading to a newer, unaffected firmware version or replacing the device with a more secure model. 3) Restrict remote management access to the router by disabling remote administration features or limiting access to trusted IP addresses only. 4) Implement network segmentation to isolate vulnerable devices from critical internal systems, reducing the attack surface. 5) Monitor network traffic for unusual activity or signs of exploitation attempts targeting the /goform/PPTPUserSetting endpoint. 6) Employ intrusion detection/prevention systems (IDS/IPS) with signatures that can detect exploitation attempts of this buffer overflow. 7) Educate IT staff about this vulnerability and ensure incident response plans include steps for handling router compromises. 8) Consider deploying network-level protections such as firewall rules to block unsolicited traffic to vulnerable endpoints. These targeted measures go beyond generic advice by focusing on device identification, access control, monitoring, and network architecture adjustments specific to this vulnerability.