CVE-2026-7057: Tenda F456 Buffer Overflow Vulnerability

CVE-2026-7057 Overview

CVE-2026-7057 is a buffer overflow vulnerability in the Tenda F456 router running firmware version 1.0.0.5. The flaw resides in an unknown function within the /goform/setcfm endpoint of the httpd component. Attackers can trigger memory corruption by manipulating the funcname or funcpara1 arguments sent to the affected endpoint. The vulnerability is exploitable remotely over the network and a public exploit has been disclosed. The weakness is tracked under CWE-119, covering improper restriction of operations within memory buffer bounds.

Critical Impact
Remote attackers with low-level privileges can corrupt memory in the router's web server, potentially leading to denial of service or arbitrary code execution on the device.

Affected Products

Tenda F456 router (hardware)
Tenda F456 Firmware version 1.0.0.5
The httpd component handling /goform/setcfm requests

Discovery Timeline

2026-04-26 - CVE-2026-7057 published to NVD
2026-04-29 - Last updated in NVD database

Technical Details for CVE-2026-7057

Vulnerability Analysis

The vulnerability is a classic stack or heap buffer overflow in the embedded web server (httpd) of the Tenda F456 router. The /goform/setcfm handler processes HTTP POST parameters funcname and funcpara1 without proper bounds checking. When an attacker submits oversized input for either parameter, the underlying string handling routine writes past the allocated buffer boundary. This overwrites adjacent memory, including potentially sensitive control structures such as return addresses or function pointers used by the httpd process.

Because the affected binary typically runs with elevated privileges on the device, successful exploitation grants the attacker meaningful control over the router. The attack vector is the network, and exploitation does not require user interaction.

Root Cause

The root cause is the absence of length validation on user-supplied parameters before they are copied into fixed-size buffers. Functions in the goform handler family in Tenda devices have historically used unsafe operations such as strcpy or sprintf on HTTP form data. Without enforcing a maximum input size, the routine writes attacker-controlled bytes beyond the destination buffer, satisfying the conditions described in CWE-119.

Attack Vector

An attacker sends a crafted HTTP request to the router's management interface targeting /goform/setcfm. The request includes an oversized value in funcname or funcpara1. Because the vulnerability requires authentication at a low privilege level, an attacker who has obtained any valid credentials, or who reaches an exposed management interface with default credentials, can deliver the payload. The public proof-of-concept is documented in the GitHub PoC Repository and tracked in VulDB #359630.

No verified exploit code is reproduced here. Refer to the linked references for technical proof-of-concept details.

Detection Methods for CVE-2026-7057

Indicators of Compromise

HTTP POST requests to /goform/setcfm containing unusually long funcname or funcpara1 parameter values
Unexpected httpd process crashes, restarts, or watchdog-triggered reboots on the Tenda F456
Outbound connections from the router to unfamiliar IP addresses following management interface access
New or modified configuration entries on the device that do not match administrative change records

Detection Strategies

Inspect web traffic destined for the router for POST requests targeting /goform/setcfm with parameter lengths exceeding typical configuration values
Deploy network intrusion detection signatures that flag oversized funcname and funcpara1 arguments on Tenda HTTP endpoints
Correlate router syslog events showing httpd crashes with preceding HTTP requests from the LAN or WAN
Monitor for repeated authentication attempts followed by anomalous POST traffic to goform handlers

Monitoring Recommendations

Forward router syslog and authentication events to a centralized logging or SIEM platform for correlation
Track baseline request sizes for /goform/* endpoints and alert on statistical outliers
Audit which internal hosts communicate with the router management interface to identify unusual sources
Periodically verify firmware integrity and configuration state against a known-good baseline

How to Mitigate CVE-2026-7057

Immediate Actions Required

Restrict access to the Tenda F456 management interface to trusted management VLANs and disable WAN-side administration
Change default and weak administrative credentials to long, unique passwords
Block external HTTP and HTTPS access to the router from untrusted networks at the upstream firewall
Inventory all Tenda F456 devices running firmware 1.0.0.5 and prioritize them for replacement or isolation

Patch Information

At the time of publication, no vendor advisory or fixed firmware version has been published on the Tenda Homepage for this issue. Administrators should monitor the vendor support portal for an updated firmware release addressing the httpd/goform/setcfm handler. Track the entry in VulDB #359630 for status updates.

Workarounds

Place affected routers behind a network segmentation boundary that blocks untrusted access to TCP ports 80 and 443 on the device
Disable remote management features and any UPnP services that expose the web interface
Replace end-of-support Tenda F456 devices with currently maintained models when no patch is available
Apply ACLs on upstream switches or firewalls to permit management traffic only from designated administrator workstations

bash

# Example upstream firewall ACL restricting router management access
# Replace with values appropriate for your environment
iptables -A FORWARD -p tcp -d 192.0.2.1 --dport 80 \
  -s 10.10.20.0/24 -j ACCEPT
iptables -A FORWARD -p tcp -d 192.0.2.1 --dport 80 -j DROP
iptables -A FORWARD -p tcp -d 192.0.2.1 --dport 443 \
  -s 10.10.20.0/24 -j ACCEPT
iptables -A FORWARD -p tcp -d 192.0.2.1 --dport 443 -j DROP