CVE-2025-7794: Tenda FH451 Buffer Overflow Vulnerability

CVE-2025-7794 Overview

CVE-2025-7794 is a stack-based buffer overflow vulnerability in the Tenda FH451 router running firmware version 1.0.0.9. The flaw resides in the fromNatStaticSetting function handling requests to the /goform/NatStaticSetting endpoint. An attacker can manipulate the page parameter to overflow a fixed-size stack buffer. The attack is reachable over the network and requires only low-level authentication. Public disclosure of the exploit increases the risk of opportunistic attacks against exposed devices.

Critical Impact

Remote attackers can corrupt stack memory in the router's web management interface, potentially leading to arbitrary code execution, device compromise, or denial of service against the affected Tenda FH451 device.

Affected Products

• Tenda FH451 router (hardware)
• Tenda FH451 firmware version 1.0.0.9
• Web management interface endpoint /goform/NatStaticSetting

Discovery Timeline

• 2025-07-18 - CVE-2025-7794 published to NVD
• 2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-7794

Vulnerability Analysis

The vulnerability is a classic stack-based buffer overflow [CWE-119] in the HTTP handler fromNatStaticSetting. This function processes configuration requests for static NAT rules via the /goform/NatStaticSetting endpoint. The handler reads the page query parameter from the incoming HTTP request and copies it into a fixed-size stack buffer without validating the input length. When an attacker supplies an oversized page value, the copy operation writes past the buffer boundary and corrupts adjacent stack memory, including saved return addresses.

Successful exploitation can hijack control flow within the router's httpd process. On embedded MIPS or ARM-based SOHO devices like the FH451, attackers commonly chain such overflows with ROP gadgets to execute shellcode. Reliable exploitation typically yields code execution as the web server user, which on consumer routers is frequently root.

Root Cause

The root cause is missing bounds checking on user-controlled input before performing a stack copy operation. The fromNatStaticSetting function trusts the length of the page parameter supplied by the client. Without validation against the destination buffer size, the handler permits memory corruption on any oversized request.

Attack Vector

The attack is launched remotely over the network against the router's HTTP management interface. The attacker sends a crafted HTTP request to /goform/NatStaticSetting with an oversized page parameter. Exploitation requires a session with low-level privileges on the web interface. No user interaction is required once the attacker can reach the management endpoint.

The vulnerability manifests when the handler processes the request and copies the attacker-controlled page value into a stack buffer. See the GitHub Vulnerability Documentation and VulDB #316855 Details for proof-of-concept details.

Detection Methods for CVE-2025-7794

Indicators of Compromise

• HTTP POST or GET requests to /goform/NatStaticSetting containing unusually long page parameter values
• Repeated crashes or restarts of the httpd process on the Tenda FH451 router
• Unexpected outbound connections originating from the router after receiving requests to the NAT configuration endpoint
• Authentication log entries from low-privilege accounts followed by anomalous administrative actions

Detection Strategies

• Inspect HTTP traffic targeting /goform/NatStaticSetting and flag parameter values exceeding typical lengths (for example, more than 256 bytes for page)
• Monitor the router's syslog output for segmentation faults, watchdog resets, or httpd respawn events
• Deploy network IDS signatures matching oversized query strings against Tenda goform endpoints

Monitoring Recommendations

• Forward router syslog and management interface access logs to a central SIEM for correlation
• Alert on any administrative access to FH451 devices from untrusted source IP addresses
• Track firmware version inventory across deployed Tenda devices to identify unpatched units running 1.0.0.9

How to Mitigate CVE-2025-7794

Immediate Actions Required

• Restrict access to the FH451 web management interface to trusted internal management VLANs only
• Disable WAN-side remote management on all FH451 devices to prevent internet-based exploitation
• Rotate administrative credentials and remove any unused low-privilege accounts that could be abused for authenticated exploitation
• Place affected devices behind a network firewall that filters traffic to /goform/NatStaticSetting

Patch Information

At the time of publication, Tenda has not released a fixed firmware version addressing CVE-2025-7794. Monitor the Tenda Official Website for firmware updates. Until a patch is available, treat the device as vulnerable and apply compensating network controls.

Workarounds

• Segment the router's management plane from user networks using VLANs or dedicated management interfaces
• Block external access to TCP ports used by the FH451 HTTP management interface at the perimeter
• Replace internet-exposed FH451 units with patched or alternative hardware where feasible
• Apply web application firewall rules that drop requests with oversized parameters to goform endpoints

# Example iptables rule restricting FH451 management access to a trusted subnet
iptables -A INPUT -p tcp --dport 80 -s 10.10.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 10.10.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP