CVE-2024-51311: Critical Stack Overflow in Tenda TX9 Router Firmware

Executive Summary

A critical stack overflow vulnerability (CVE-2024-51311) has been identified in the Tenda TX9 Wi-Fi 6 router running firmware version V22.03.02.05. The flaw resides in the sub_4418CC function within the /goform/SetNetControlList handler, where unsanitized user input can overflow the stack and overwrite control data — enabling remote code execution without authentication.

CVSS Score: 9.8 (Critical)

Tenda SOHO routers have historically been targeted in botnet campaigns (Mirai variants, VPNFilter). A publicly accessible management interface combined with a CVSS 9.8 stack overflow makes this a high-priority patching target for home and small-business environments.

Vulnerability Overview

Affected Products

No patched firmware version has been publicly announced at the time of publication. Check the Tenda support portal for updates.

Technical Analysis

The vulnerability is a classic stack-based buffer overflow in the router's web management interface. When a POST request is sent to /goform/SetNetControlList, the function sub_4418CC copies user-supplied data into a fixed-size stack buffer without validating the input length. An attacker can send an oversized payload to:

1. Overflow the stack buffer
2. Overwrite the saved return address
3. Redirect execution to attacker-controlled shellcode or ROP gadgets
4. Achieve full code execution on the MIPS-based router CPU

Attack flow:

POST /goform/SetNetControlList HTTP/1.1
Host: <router-ip>
Content-Type: application/x-www-form-urlencoded

netControlList=<OVERSIZED_PAYLOAD>

Because SOHO routers typically lack modern exploit mitigations (ASLR, stack canaries, NX enforcement in firmware), exploitation is often straightforward once the overflow offset is determined.

Risk Context

Tenda routers have been a recurring target for botnet operators:

• Mirai and its derivatives routinely sweep for Tenda vulnerabilities to recruit routers into DDoS infrastructure
• VPNFilter (attributed to Sandworm/APT28) targeted Tenda devices in its 2018 campaign affecting 500,000+ routers
• Shodan and Censys scans consistently reveal tens of thousands of Tenda management interfaces exposed to the public internet

A CVSS 9.8 network-exploitable RCE with no authentication required will likely attract automated exploitation within days of public disclosure.

Immediate Remediation

Step 1: Disable Remote Management

If firmware update is unavailable, disable remote (WAN-side) management access immediately:

1. Log into the router admin panel (default: 192.168.0.1)
2. Navigate to Advanced → Remote Management
3. Disable WAN-side admin access

Step 2: Restrict LAN-Side Access

Even on the LAN, limit which devices can access the management interface:

# From the router's access control settings, restrict admin access to a single management host
# or use a separate VLAN for management traffic

Step 3: Monitor for Firmware Updates

# Check current firmware version from router admin panel
# Compare against Tenda's firmware download page for TX9
# Apply any available update immediately

Step 4: Network Segmentation

Place affected routers behind a firewall and isolate them from critical network segments until a patch is available.

Detection

SNORT/Suricata rule hint:

alert tcp any any -> $HOME_NET 80 (msg:"Tenda TX9 CVE-2024-51311 overflow attempt"; content:"POST"; http_method; content:"/goform/SetNetControlList"; http_uri; dsize:>512; sid:9999999; rev:1;)

Workarounds

If patching is not immediately possible:

1. Block public access to the router management interface at the ISP or upstream firewall level
2. Change default credentials — credential stuffing often precedes exploitation
3. Enable router logging to a remote syslog server for visibility
4. Consider replacement — if the device is end-of-support, evaluate replacing with a supported model

References

• NVD — CVE-2024-51311
• Tenda TX9 Product Page
• Tenda Firmware Downloads

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