CVE-2025-7806: Tenda FH451 Buffer Overflow Vulnerability

CVE-2025-7806 Overview

CVE-2025-7806 is a stack-based buffer overflow vulnerability in the Tenda FH451 router firmware version 1.0.0.9. The flaw resides in the fromSafeClientFilter function, which handles requests to the /goform/SafeClientFilter endpoint. Manipulation of the Go or page parameters triggers a stack-based buffer overflow [CWE-119]. The vulnerability is exploitable remotely over the network and requires low privileges. Public disclosure of the exploit details has occurred through third-party vulnerability databases and GitHub repositories.

Critical Impact
Remote attackers with low-privileged access can corrupt the stack of the Tenda FH451 router, potentially leading to arbitrary code execution and full device compromise.

Affected Products

Tenda FH451 router (hardware)
Tenda FH451 firmware version 1.0.0.9
Devices exposing the /goform/SafeClientFilter web management endpoint

Discovery Timeline

2025-07-18 - CVE-2025-7806 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-7806

Vulnerability Analysis

The vulnerability exists in the fromSafeClientFilter function within the Tenda FH451 web management interface. This function processes HTTP requests sent to /goform/SafeClientFilter, which configures client filtering rules on the router. The function copies attacker-controlled values from the Go and page request parameters into fixed-size stack buffers without enforcing length checks.

When an attacker submits an overly long string in either parameter, the copy operation overruns the destination buffer and overwrites adjacent stack memory. This includes saved registers and the return address of the calling function. Successful exploitation can redirect execution flow, enabling arbitrary code execution in the context of the router's web service, which typically runs with elevated privileges on embedded MIPS or ARM platforms.

Root Cause

The root cause is the absence of bounds checking when handling user-supplied input within fromSafeClientFilter. The function relies on unsafe string-copy operations against fixed-size stack buffers, a classic [CWE-119] improper restriction of operations within the bounds of a memory buffer. Tenda's consumer and SOHO router firmware has a recurring pattern of similar issues across /goform/* handlers.

Attack Vector

The attack is network-based and requires authenticated access to the router's management interface. An attacker sends a crafted HTTP POST request to /goform/SafeClientFilter with an oversized value for the Go or page argument. If management access is exposed to the WAN or the attacker is on the LAN, exploitation is straightforward. Reference proof-of-concept material is published in the panda666-888 vuls repository - Go parameter and panda666-888 vuls repository - page parameter.

No verified exploitation code is reproduced here. The referenced advisories describe the request structure and the overflowed parameters used to trigger the crash. See VulDB entry #316882 for additional technical metadata.

Detection Methods for CVE-2025-7806

Indicators of Compromise

HTTP POST requests to /goform/SafeClientFilter containing abnormally long Go or page parameter values
Unexpected reboots or crashes of the Tenda FH451 web management daemon (httpd)
Unauthorized configuration changes to client filtering rules or new administrative sessions originating from untrusted IPs
Outbound connections from the router to unknown command-and-control infrastructure following management interface access

Detection Strategies

Inspect HTTP traffic to the router management interface and alert on requests to /goform/SafeClientFilter where parameter lengths exceed expected bounds (typically under 128 bytes)
Deploy network IDS signatures that flag long parameter strings against Tenda /goform/* endpoints
Monitor router syslog output for httpd segmentation faults, watchdog-triggered reboots, or repeated authentication anomalies

Monitoring Recommendations

Forward router syslog and authentication events to a centralized SIEM for correlation against management interface access patterns
Baseline normal administrative request volumes to /goform/* endpoints and alert on deviations
Track all source IPs that authenticate to the router and flag access from outside designated management subnets

How to Mitigate CVE-2025-7806

Immediate Actions Required

Restrict access to the router's web management interface to trusted LAN segments only and disable remote WAN management
Change default and weak administrative credentials, since exploitation requires authenticated access
Segment the FH451 from sensitive network zones until a vendor patch is available
Audit recent management traffic logs for indicators of attempted exploitation against /goform/SafeClientFilter

Patch Information

At the time of publication, no vendor security advisory or firmware update from Tenda has been linked in the NVD record for CVE-2025-7806. Administrators should monitor the Tenda official website for firmware updates addressing the fromSafeClientFilter function. If the FH451 is end-of-life or no patch is forthcoming, consider replacing the device with a supported model.

Workarounds

Disable the web management interface entirely if router configuration can be performed out-of-band
Place the router behind an upstream firewall and apply an ACL restricting TCP access to the management port to a single jump host
Disable any unused client filtering features that route through /goform/SafeClientFilter
Where supported, enable account lockout policies to limit brute-force attempts that would precede exploitation

bash

# Example upstream firewall ACL restricting Tenda FH451 management access
# Replace 192.0.2.10 with the trusted admin workstation IP
# Replace 10.0.0.1 with the Tenda FH451 LAN IP
iptables -A FORWARD -p tcp -s 192.0.2.10 -d 10.0.0.1 --dport 80 -j ACCEPT
iptables -A FORWARD -p tcp -d 10.0.0.1 --dport 80 -j DROP
iptables -A FORWARD -p tcp -d 10.0.0.1 --dport 443 -j DROP