CVE-2025-57569: Tenda F3 Buffer Overflow Vulnerability

CVE-2025-57569 Overview

CVE-2025-57569 is a buffer overflow vulnerability affecting Tenda F3 routers running firmware version V12.01.01.48_multi and later. The flaw resides in the /goform/setNAT endpoint, where the portList parameter is processed without adequate bounds checking. Remote attackers can send crafted HTTP requests over the network to trigger memory corruption in the router's web management interface. The vulnerability is classified under [CWE-120] (Buffer Copy without Checking Size of Input).

Critical Impact
Successful exploitation can corrupt memory on the affected router, leading to service disruption and potentially unauthorized code execution within the embedded firmware context.

Affected Products

Tenda F3 router hardware
Tenda F3 firmware version V12.01.01.48_multi
Tenda F3 firmware versions released after V12.01.01.48_multi

Discovery Timeline

2025-09-10 - CVE-2025-57569 published to the National Vulnerability Database (NVD)
2026-07-05 - Last updated in NVD database

Technical Details for CVE-2025-57569

Vulnerability Analysis

The Tenda F3 router exposes a web-based configuration interface that handles Network Address Translation (NAT) rules through the /goform/setNAT handler. The handler accepts a portList parameter supplied by the client during NAT configuration requests. The firmware copies this parameter into a fixed-size stack or heap buffer without validating the input length against the destination buffer capacity.

Attackers can supply an oversized portList value to overwrite adjacent memory regions. Depending on the memory layout, this corruption can crash the httpd process, disrupt router functionality, or overwrite return addresses and function pointers. The attack requires network access to the router's management interface but does not require authentication or user interaction.

Root Cause

The root cause is missing bounds validation on attacker-controlled input before it is copied into a bounded buffer. The firmware trusts the length of the portList HTTP parameter and performs an unchecked copy operation, which matches the [CWE-120] classification for classic buffer overflow.

Attack Vector

Exploitation occurs remotely over the network. An attacker sends a specially crafted HTTP POST request to /goform/setNAT containing an overly long portList value. Because the vulnerability affects an embedded router, the attacker often needs access to the LAN or a WAN-exposed management interface. A public proof-of-concept is available in the GitHub PoC for CVE-2025-57569 repository.

// No verified exploitation code is reproduced here.
// Refer to the linked PoC repository for technical details.

Detection Methods for CVE-2025-57569

Indicators of Compromise

Unexpected reboots or httpd process crashes on Tenda F3 routers
HTTP POST requests to /goform/setNAT containing abnormally long portList parameter values
Loss of management interface availability following configuration requests from unknown sources

Detection Strategies

Inspect network traffic to the router management interface for POST requests targeting /goform/setNAT with portList payloads exceeding expected length limits
Deploy intrusion detection signatures that flag oversized parameters directed at Tenda goform endpoints
Correlate router syslog crash events with recent inbound HTTP requests to identify exploitation attempts

Monitoring Recommendations

Forward router logs to a centralized log platform to preserve crash and reboot evidence for forensic review
Monitor for scanning activity targeting Tenda web interfaces on TCP ports 80 and 443 across internal networks
Alert on any WAN-side access attempts to the router administration interface

How to Mitigate CVE-2025-57569

Immediate Actions Required

Restrict access to the Tenda F3 web management interface to trusted LAN hosts only
Disable remote WAN management on affected routers until a vendor patch is released
Replace end-of-life or unsupported Tenda F3 units with actively maintained hardware where feasible

Patch Information

No vendor advisory or security patch has been published for CVE-2025-57569 at the time of writing. Administrators should monitor the Tenda support portal for firmware updates addressing the /goform/setNAT handler.

Workarounds

Place the router management interface behind a firewall rule that only permits administrative source IPs
Segment the router administration VLAN from user and guest networks to reduce internal attack surface
Disable UPnP and unnecessary NAT configuration features that expose the setNAT handler to untrusted clients

bash

# Example: block external access to Tenda web interface on an upstream firewall
iptables -A FORWARD -p tcp --dport 80 -d <router_ip> -j DROP
iptables -A FORWARD -p tcp --dport 443 -d <router_ip> -j DROP