CVE-2025-7796 in FH451
Summary
by MITRE • 07/18/2025
A vulnerability, which was classified as critical, was found in Tenda FH451 1.0.0.9. This affects the function fromPptpUserAdd of the file /goform/PPTPDClient. The manipulation of the argument Username leads to stack-based buffer overflow. It is possible to initiate the attack remotely. The exploit has been disclosed to the public and may be used.
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Analysis
by VulDB Data Team • 07/23/2025
The vulnerability identified as CVE-2025-7796 represents a critical stack-based buffer overflow in the Tenda FH451 router firmware version 1.0.0.9. This flaw exists within the PPTPDClient component, specifically in the fromPptpUserAdd function located at /goform/PPTPDClient. The vulnerability stems from inadequate input validation when processing the Username argument, creating a condition where maliciously crafted input can exceed the allocated buffer space on the stack. The issue is particularly concerning as it allows for remote exploitation, meaning attackers can trigger the vulnerability without requiring physical access to the device. This remote attack vector significantly expands the potential impact and attack surface, making the vulnerability particularly dangerous in networked environments where routers serve as critical infrastructure components.
The technical exploitation of this buffer overflow vulnerability follows established patterns described in CWE-121, which catalogs stack-based buffer overflow conditions. When an attacker supplies a Username argument that exceeds the buffer's allocated size, the excess data overflows into adjacent memory locations, potentially overwriting critical program execution data such as return addresses, stack canaries, or function pointers. This memory corruption can lead to arbitrary code execution, privilege escalation, or complete system compromise. The vulnerability's classification as critical aligns with CVSS scoring criteria that consider remote exploitability, the presence of a publicly disclosed exploit, and the potential for system-level compromise. The attack can be initiated through the web-based management interface of the router, leveraging the HTTP form submission mechanism that processes the PPTPDClient requests.
The operational impact of CVE-2025-7796 extends beyond simple denial of service scenarios, as the vulnerability could enable attackers to gain persistent access to network infrastructure. Once exploited, an attacker could potentially establish a backdoor, redirect network traffic, modify router configurations, or use the compromised device as a launch point for further attacks against internal network resources. The PPTP client functionality is commonly used for remote access VPN connections, making this vulnerability particularly dangerous in corporate environments where such services are deployed. The publicly disclosed exploit status means that threat actors do not require advanced technical skills to leverage the vulnerability, increasing the likelihood of widespread exploitation. Organizations with affected Tenda FH451 devices face immediate risk of network infiltration and data breaches, particularly in environments where router security is not adequately monitored or updated.
Mitigation strategies for CVE-2025-7796 must be implemented immediately given the critical nature of the vulnerability. The primary recommendation involves applying the latest firmware update from Tenda, which should contain a patch addressing the buffer overflow condition through proper input validation and bounds checking. Network administrators should also implement network segmentation to limit access to router management interfaces, restrict remote access to essential personnel only, and deploy intrusion detection systems to monitor for exploitation attempts. Additional defensive measures include disabling unnecessary services such as PPTP client functionality if not required, implementing strong authentication mechanisms, and conducting comprehensive network scans to identify potentially compromised devices. The vulnerability's presence in the web interface also necessitates web application firewall rules that can detect and block malicious input patterns targeting the affected form processing endpoint. Organizations should also consider implementing network access controls that restrict which external IP addresses can reach router management interfaces, thereby reducing the attack surface for remote exploitation attempts.