CVE-2026-3804 Overview
A critical stack-based buffer overflow vulnerability has been discovered in Tenda i3 firmware version 1.0.0.6(2204). This vulnerability affects the formWifiMacFilterSet function within the /goform/WifiMacFilterSet file. Through manipulation of the index argument, attackers can trigger a stack-based buffer overflow condition. The vulnerability is remotely exploitable, and a public exploit has been released, significantly increasing the risk of active exploitation in the wild.
Critical Impact
Remote attackers with low privileges can exploit this stack-based buffer overflow to achieve high impact on confidentiality, integrity, and availability of affected Tenda i3 devices. The public availability of exploit code increases the urgency for immediate remediation.
Affected Products
- Tenda i3 Firmware version 1.0.0.6(2204)
- Tenda i3 hardware devices running vulnerable firmware
- Network environments deploying affected Tenda i3 access points
Discovery Timeline
- 2026-03-09 - CVE-2026-3804 published to NVD
- 2026-03-09 - Last updated in NVD database
Technical Details for CVE-2026-3804
Vulnerability Analysis
This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), which indicates fundamental memory safety issues in the affected firmware. The vulnerability exists in the formWifiMacFilterSet function, which handles WiFi MAC filtering configuration requests through the web interface.
When processing the index parameter, the function fails to properly validate input length before copying data into a fixed-size stack buffer. This allows an attacker to provide an overly long value that exceeds the allocated buffer space, overwriting adjacent stack memory including return addresses and other critical control flow data.
The network-accessible attack vector combined with low attack complexity makes this vulnerability particularly dangerous for exposed Tenda i3 devices. Successful exploitation can lead to complete device compromise, including arbitrary code execution with the privileges of the web server process.
Root Cause
The root cause stems from improper bounds checking in the formWifiMacFilterSet function when processing the index argument. The firmware uses unsafe string handling functions that do not verify the length of user-supplied input before copying it to a stack-allocated buffer. This classic memory corruption pattern allows attackers to overflow the buffer boundaries and corrupt adjacent stack memory.
Attack Vector
The attack can be executed remotely over the network against the device's web management interface at /goform/WifiMacFilterSet. An attacker with low-level privileges (authenticated access to the web interface) can craft a malicious HTTP request containing an oversized index parameter value.
The exploitation flow typically involves:
- Authenticating to the Tenda i3 web management interface
- Sending a crafted POST request to /goform/WifiMacFilterSet
- Including a maliciously long index parameter that overflows the stack buffer
- Overwriting the return address to redirect execution flow
- Achieving arbitrary code execution on the device
For detailed technical analysis and proof-of-concept information, refer to the GitHub PoC Repository.
Detection Methods for CVE-2026-3804
Indicators of Compromise
- Unusual HTTP POST requests to /goform/WifiMacFilterSet with abnormally long parameter values
- Device crashes or unexpected reboots following web interface access
- Unauthorized configuration changes to WiFi MAC filtering settings
- Anomalous network traffic originating from Tenda i3 devices
Detection Strategies
- Monitor web server logs for requests to /goform/WifiMacFilterSet with unusually large index parameter values
- Implement network intrusion detection rules to identify buffer overflow attack patterns targeting Tenda devices
- Deploy deep packet inspection to analyze HTTP traffic destined for device management interfaces
- Configure alerting for multiple failed or malformed requests to device administration endpoints
Monitoring Recommendations
- Enable detailed logging on network firewalls for traffic to Tenda device management ports
- Implement anomaly detection for HTTP request sizes exceeding normal thresholds to device endpoints
- Monitor device health metrics for unexpected resource consumption or service interruptions
- Establish baseline behavior for device web interface access patterns to identify deviations
How to Mitigate CVE-2026-3804
Immediate Actions Required
- Restrict network access to Tenda i3 management interfaces using firewall rules or network segmentation
- Disable remote management access if not required for operations
- Place affected devices behind VPN or jump hosts to limit exposure
- Monitor devices for signs of compromise while awaiting vendor patches
Patch Information
At the time of publication, no official patch from Tenda has been identified for this vulnerability. Organizations should monitor the Tenda Official Website for security updates and firmware releases addressing CVE-2026-3804. Additional vulnerability details are available at VulDB #349771.
Workarounds
- Implement strict access control lists (ACLs) to limit which IP addresses can reach the device management interface
- Deploy a web application firewall (WAF) to filter requests with oversized parameters targeting /goform/WifiMacFilterSet
- Consider device replacement with alternative hardware from vendors with stronger security update practices
- Isolate affected devices on a separate network segment with enhanced monitoring
# Example firewall rule to restrict management interface access
# Allow only trusted management network (adjust IPs as needed)
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
# Block external access to vulnerable endpoint at network perimeter
# (Implementation varies by firewall vendor)
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
