CVE-2024-3874: Tenda W20e Buffer Overflow Vulnerability

CVE-2024-3874 Overview

CVE-2024-3874 is a stack-based buffer overflow in the Tenda W20E router firmware version 15.11.0.6. The flaw resides in the formSetRemoteWebManage function within the /goform/SetRemoteWebManage endpoint. Attackers can trigger memory corruption by manipulating the remoteIP parameter over the network. Successful exploitation can lead to arbitrary code execution or a denial-of-service condition on the affected device. The exploit details have been publicly disclosed, increasing the risk of opportunistic attacks against exposed devices. The vendor was contacted before disclosure but did not respond, and no official patch is available at the time of publication.

Critical Impact
Authenticated remote attackers can corrupt stack memory on Tenda W20E routers, potentially executing arbitrary code or causing device crashes affecting network availability.

Affected Products

Tenda W20E router (hardware)
Tenda W20E firmware version 15.11.0.6
Deployments exposing the /goform/SetRemoteWebManage endpoint

Discovery Timeline

2024-04-16 - CVE-2024-3874 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-3874

Vulnerability Analysis

The vulnerability is a stack-based buffer overflow classified under [CWE-121] and [CWE-787]. The formSetRemoteWebManage handler processes the remoteIP HTTP parameter without validating its length before copying it into a fixed-size stack buffer. An attacker who submits an oversized remoteIP value overwrites adjacent stack memory, including saved return addresses and function pointers.

The endpoint /goform/SetRemoteWebManage typically controls remote web management settings on the router. Because the flaw affects a management interface, exploitation impacts the confidentiality, integrity, and availability of the device. Successful control of the instruction pointer can enable arbitrary code execution in the context of the web management service, which commonly runs with elevated privileges on embedded devices.

The attack requires network access to the router's management interface and low-level authentication credentials. Where remote management is enabled on the WAN interface, attackers can reach the vulnerable endpoint from the internet.

Root Cause

The root cause is missing bounds checking on the remoteIP argument inside formSetRemoteWebManage. The function relies on unsafe string handling routines that copy attacker-controlled input into a stack buffer without enforcing a maximum length. This pattern is common in Tenda web management binaries and consistently produces exploitable memory corruption.

Attack Vector

An attacker sends a crafted HTTP request to /goform/SetRemoteWebManage with an oversized remoteIP parameter. The malformed value overflows the destination buffer during processing. Depending on payload construction, the outcome ranges from a crash of the management service to full control of program execution. Public proof-of-concept details are available in the GitHub IoT Vulnerability Report and the VulDB Entry #260908.

See the referenced advisories for technical details on the exact payload structure and offset calculations.

Detection Methods for CVE-2024-3874

Indicators of Compromise

HTTP POST requests to /goform/SetRemoteWebManage containing abnormally long remoteIP parameter values
Unexpected restarts or crashes of the router's web management daemon
Repeated authentication attempts followed by malformed requests to goform endpoints
Outbound connections initiated by the router to unfamiliar IP addresses following management traffic

Detection Strategies

Inspect HTTP traffic destined for router management interfaces and flag remoteIP values exceeding realistic IPv4 or IPv6 string lengths
Deploy network intrusion detection signatures that match oversized parameters in Tenda goform requests
Correlate router syslog events showing service restarts with preceding management-interface traffic

Monitoring Recommendations

Log all administrative access to Tenda W20E devices and forward logs to a centralized analytics platform
Alert on any WAN-side connections to router management ports (typically TCP 80 and TCP 443)
Baseline normal management traffic patterns and alert on statistically anomalous request payload sizes

How to Mitigate CVE-2024-3874

Immediate Actions Required

Disable remote web management on the WAN interface until a vendor patch is available
Restrict management access to a trusted internal VLAN or specific administrator source IP addresses
Rotate router administrator credentials and enforce strong password policies
Segment IoT and network infrastructure devices from user and server networks

Patch Information

No official patch has been released by Tenda at the time of publication. The vendor did not respond to disclosure attempts referenced in VulDB CTI ID 260908. Monitor the Tenda security portal for firmware updates addressing CVE-2024-3874, and apply updates immediately upon release.

Workarounds

Turn off the remote web management feature entirely if the deployment does not require it
Place the router behind an upstream firewall that blocks inbound TCP 80 and TCP 443 to the device
Replace end-of-support or unpatched Tenda W20E devices with actively maintained hardware
Use a VPN for administrative access rather than exposing the management interface to the internet

bash

# Example: Block inbound WAN access to router management ports on an upstream firewall
iptables -A FORWARD -p tcp -d <router_wan_ip> --dport 80 -j DROP
iptables -A FORWARD -p tcp -d <router_wan_ip> --dport 443 -j DROP

# Verify remote management is disabled via the router admin UI:
# Advanced Settings > System Tools > Remote Web Management > Disabled