CVE-2025-7807: Tenda FH451 Buffer Overflow Vulnerability

CVE-2025-7807 Overview

CVE-2025-7807 is a stack-based buffer overflow vulnerability affecting Tenda FH451 routers running firmware version 1.0.0.9. The flaw resides in the fromSafeUrlFilter function within the /goform/SafeUrlFilter endpoint. Attackers can trigger the overflow by manipulating the Go or page arguments sent to this endpoint. The vulnerability is remotely exploitable over the network and a public proof-of-concept has been disclosed. The weakness is categorized under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer).

Critical Impact
Remote attackers with low-privilege access can corrupt stack memory on Tenda FH451 routers, potentially leading to arbitrary code execution or denial of service against the device.

Affected Products

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

Discovery Timeline

2025-07-18 - CVE-2025-7807 published to NVD
2025-07-23 - Last updated in NVD database

Technical Details for CVE-2025-7807

Vulnerability Analysis

The vulnerability exists in the fromSafeUrlFilter function, which handles HTTP requests sent to /goform/SafeUrlFilter on the Tenda FH451 web management interface. The function processes user-supplied values from the Go and page request parameters without enforcing proper bounds checking. When attacker-controlled data is copied into a fixed-size stack buffer, the write operation exceeds the allocated boundary and overwrites adjacent stack memory, including saved return addresses.

Public proof-of-concept material on GitHub demonstrates that the overflow is reachable through standard HTTP requests against the management interface. Successful exploitation can crash the httpd process, disrupting network services. On embedded MIPS or ARM router platforms without modern exploit mitigations, controlled corruption of the saved return address may enable arbitrary code execution as the web server process, which typically runs with elevated privileges on consumer routers.

Root Cause

The root cause is missing or insufficient length validation on the Go and page HTTP parameters before they are copied into a stack-allocated buffer. The function does not enforce a maximum length consistent with the destination buffer size, allowing a long input to overrun the buffer.

Attack Vector

The vulnerability is exploitable over the network by sending a crafted HTTP request to the /goform/SafeUrlFilter endpoint. The CVSS vector indicates that low-level authentication is required, meaning an attacker needs valid management credentials or access to a session, but no user interaction is needed. Routers with default credentials or exposed management interfaces are at heightened risk.

// Conceptual request shape - see linked PoC repositories for full details
POST /goform/SafeUrlFilter HTTP/1.1
Host: <router-ip>
Content-Type: application/x-www-form-urlencoded

Go=<oversized payload>&page=<oversized payload>

Full technical details are documented in the GitHub PoC for the Go parameter and the GitHub PoC for the page parameter.

Detection Methods for CVE-2025-7807

Indicators of Compromise

HTTP POST requests to /goform/SafeUrlFilter containing abnormally long values in the Go or page parameters
Unexpected restarts or crashes of the httpd process on Tenda FH451 routers
Outbound connections from the router to unknown infrastructure following management-interface activity
Configuration changes on the router that do not align with administrator activity

Detection Strategies

Inspect HTTP request bodies destined for /goform/SafeUrlFilter and flag parameter lengths that exceed expected limits
Monitor router syslog or remote logging for repeated web server restarts or segmentation faults
Baseline normal administrative traffic to the router and alert on anomalous POST volumes against goform endpoints

Monitoring Recommendations

Forward router logs to a centralized log analytics or SIEM platform for correlation with network telemetry
Use network IDS signatures to detect oversized parameter values targeting Tenda goform URIs
Track authentication events on the router web interface to identify brute-force attempts that often precede exploitation

How to Mitigate CVE-2025-7807

Immediate Actions Required

Restrict access to the Tenda FH451 management interface to trusted internal management networks using firewall ACLs
Disable remote WAN-side management on the router if it is enabled
Rotate router administrative credentials and remove any default or shared passwords
Inventory all Tenda FH451 devices running firmware 1.0.0.9 and prioritize them for remediation

Patch Information

At the time of publication, no vendor advisory or fixed firmware version has been published on the Tenda official website for CVE-2025-7807. Administrators should monitor the vendor support pages and apply any firmware update that addresses the fromSafeUrlFilter function as soon as it becomes available. Additional tracking details are available at VulDB entry 316883.

Workarounds

Block external access to TCP ports used by the router web management interface at the perimeter
Place vulnerable routers behind a network segment that is not reachable from untrusted users or guest networks
Consider replacing end-of-support Tenda FH451 hardware if no firmware patch is released by the vendor

bash

# Example: restrict access to the router management interface to a trusted admin host
# Replace <router-ip> and <admin-ip> with your environment values
iptables -I FORWARD -p tcp -d <router-ip> --dport 80 -s <admin-ip> -j ACCEPT
iptables -I FORWARD -p tcp -d <router-ip> --dport 80 -j DROP