CVE-2026-3801 Overview
CVE-2026-3801 is a stack-based buffer overflow vulnerability in the Tenda i3 router firmware version 1.0.0.6(2204). The flaw resides in the formSetAutoPing function handling requests to the /goform/setAutoPing endpoint. Attackers can trigger the overflow by manipulating the ping1 or ping2 parameters with oversized input. The condition is categorized under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer). Public proof-of-concept code has been published, increasing the likelihood of opportunistic exploitation against exposed devices.
Critical Impact
Remote attackers with low privileges can corrupt stack memory on Tenda i3 routers, potentially leading to arbitrary code execution or denial of service against the affected network device.
Affected Products
- Tenda i3 router (hardware)
- Tenda i3 firmware version 1.0.0.6(2204)
- Devices exposing the /goform/setAutoPing web management endpoint
Discovery Timeline
- 2026-03-09 - CVE-2026-3801 published to NVD
- 2026-03-09 - Last updated in NVD database
Technical Details for CVE-2026-3801
Vulnerability Analysis
The vulnerability exists in the formSetAutoPing handler within the web management interface of the Tenda i3 router. The function processes HTTP requests submitted to /goform/setAutoPing and reads the ping1 and ping2 parameters supplied by the client. The handler copies these values into fixed-size stack buffers without enforcing length validation. Supplying parameter values longer than the destination buffer overwrites adjacent stack memory, including saved registers and the return address.
An attacker authenticated with low privileges can trigger the condition remotely by sending a crafted HTTP request. Successful exploitation can corrupt control flow on the embedded MIPS or ARM processor used by the device, leading to denial of service or arbitrary code execution within the context of the web management process. Public exploit material has been released through GitHub, lowering the barrier for reproduction.
Root Cause
The root cause is missing bounds checking on user-supplied input prior to a stack copy operation. The formSetAutoPing function uses unsafe string handling routines such as strcpy or sprintf against fixed-size local buffers. This pattern is common across Tenda /goform/* handlers and represents a systemic firmware coding issue rather than an isolated defect.
Attack Vector
Exploitation requires network access to the router web interface and valid low-privilege credentials. The attacker submits a POST request to /goform/setAutoPing containing oversized values in the ping1 or ping2 form fields. The overflow manipulates the saved return address on the stack, redirecting execution to attacker-controlled data. No user interaction is required to complete the attack chain.
The vulnerability mechanism is documented in the public proof-of-concept repositories. See the Tenda i3 ping1 PoC repository and the Tenda i3 ping2 PoC repository for technical reproduction steps.
Detection Methods for CVE-2026-3801
Indicators of Compromise
- HTTP POST requests to /goform/setAutoPing containing ping1 or ping2 parameters with abnormally long payloads (typically exceeding 100 bytes).
- Unexpected reboots, web interface crashes, or httpd process failures on Tenda i3 devices.
- Outbound connections from the router to unfamiliar external IP addresses following management interface access.
Detection Strategies
- Inspect inbound HTTP traffic to router management interfaces for requests targeting /goform/setAutoPing with oversized form parameters.
- Deploy network intrusion detection signatures that flag HTTP request bodies exceeding expected lengths for ping1 and ping2 fields.
- Correlate router log entries showing repeated authentication followed by service crashes.
Monitoring Recommendations
- Forward router syslog data to a centralized logging platform and alert on httpd segmentation faults or watchdog-triggered reboots.
- Restrict and monitor administrative access to router management interfaces from non-trusted network segments.
- Track newly published proof-of-concept exploit activity tied to VulDB entry #349768 for emerging exploitation patterns.
How to Mitigate CVE-2026-3801
Immediate Actions Required
- Disable remote (WAN-side) administration on Tenda i3 devices and restrict the management interface to trusted LAN segments only.
- Rotate administrative credentials and enforce strong, unique passwords to limit the low-privilege access prerequisite.
- Inventory deployed Tenda i3 routers running firmware 1.0.0.6(2204) and prioritize them for replacement or isolation.
Patch Information
At the time of publication, no vendor patch has been referenced in the NVD entry. Monitor the Tenda official website for firmware updates addressing the formSetAutoPing handler. If a fixed firmware version is not released, evaluate replacing affected hardware with a supported model.
Workarounds
- Place affected routers behind a perimeter firewall and block external access to TCP ports used by the web management interface.
- Apply network segmentation to limit which internal hosts can reach the router administrative interface.
- Disable the auto-ping feature in the device configuration if the deployment does not require it.
- Use an upstream web application firewall or reverse proxy to drop HTTP requests to /goform/setAutoPing containing parameters longer than expected length thresholds.
# Example firewall rule to restrict router admin interface access (Linux iptables)
iptables -A FORWARD -p tcp -d <ROUTER_IP> --dport 80 -s <TRUSTED_MGMT_SUBNET> -j ACCEPT
iptables -A FORWARD -p tcp -d <ROUTER_IP> --dport 80 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
