CVE-2026-5036 Overview
CVE-2026-5036 is a stack-based buffer overflow in the Tenda 4G06 router running firmware version 04.06.01.29. The flaw resides in the fromDhcpListClient function handling requests to the /goform/DhcpListClient endpoint. An attacker can manipulate the page argument to overflow a stack buffer, corrupting memory on the device. The vulnerability is reachable over the network and requires only low-level privileges. Public exploit details have been disclosed, increasing the risk of opportunistic attacks against exposed devices. The issue is tracked under [CWE-119] (improper restriction of operations within the bounds of a memory buffer).
Critical Impact
Remote attackers can corrupt stack memory on Tenda 4G06 routers, potentially leading to denial of service or arbitrary code execution on the affected endpoint device.
Affected Products
- Tenda 4G06 router (hardware revision 3.0)
- Tenda 4G06 firmware version 04.06.01.29
- Endpoint component exposing /goform/DhcpListClient
Discovery Timeline
- 2026-03-29 - CVE-2026-5036 published to NVD
- 2026-03-30 - Last updated in NVD database
Technical Details for CVE-2026-5036
Vulnerability Analysis
The vulnerability exists in the fromDhcpListClient function, which processes HTTP requests sent to the /goform/DhcpListClient web endpoint on the Tenda 4G06 router. The function reads the page parameter from the request and copies it into a fixed-size stack buffer without enforcing length validation. Supplying an oversized value overruns the buffer and overwrites adjacent stack data, including saved return addresses.
The weakness is categorized under [CWE-119], improper restriction of operations within the bounds of a memory buffer. Because the web server runs with elevated privileges on the embedded device, successful memory corruption can compromise the router's control plane. The attack does not require user interaction and can be repeated remotely against any reachable management interface.
Root Cause
The root cause is the absence of bounds checking when handling the page argument inside fromDhcpListClient. The handler trusts attacker-controlled input length and performs an unsafe copy into a stack-allocated buffer. Embedded MIPS-based firmware compiled without stack protection makes the overflow directly exploitable.
Attack Vector
An attacker sends a crafted HTTP request to /goform/DhcpListClient containing an overlong page parameter. If the management interface is exposed to the WAN, the attack is fully remote. On LAN-only deployments, any authenticated user or compromised internal host can trigger the overflow. Exploit details have been published, as referenced in the VulDB Vulnerability #353962 entry and GitHub Issue on CVE.
The vulnerability mechanism is described in prose only; no verified proof-of-concept code is reproduced here. Refer to the VulDB CTI Report #353962 for further technical context.
Detection Methods for CVE-2026-5036
Indicators of Compromise
- HTTP requests targeting /goform/DhcpListClient with abnormally long page query parameters.
- Unexpected reboots, crashes, or watchdog resets of Tenda 4G06 devices following inbound web requests.
- Outbound connections from the router to unfamiliar hosts, indicating possible post-exploitation activity.
Detection Strategies
- Inspect web access logs on the router or upstream proxy for requests to /goform/DhcpListClient containing oversized parameter values.
- Deploy network signatures that flag HTTP POST or GET requests with page parameter lengths exceeding expected bounds.
- Correlate device crash events with preceding HTTP traffic to identify exploitation attempts.
Monitoring Recommendations
- Capture and forward router system logs to a centralized log aggregator for analysis.
- Monitor management interface exposure and alert when WAN-side administration becomes reachable.
- Track EPSS scoring and vendor advisories for changes in active exploitation status.
How to Mitigate CVE-2026-5036
Immediate Actions Required
- Disable remote (WAN-side) administration on Tenda 4G06 devices until a vendor fix is available.
- Restrict access to /goform/DhcpListClient to trusted management hosts using ACLs or firewall rules.
- Rotate administrative credentials after confirming the device has not been compromised.
Patch Information
No vendor patch has been published in the referenced advisories at the time of NVD entry. Monitor the Tenda Security Page for firmware updates superseding version 04.06.01.29. Apply the updated firmware as soon as the vendor releases a fix addressing the fromDhcpListClient handler.
Workarounds
- Place affected routers behind a perimeter firewall and block inbound HTTP/HTTPS to the management interface.
- Segment IoT and consumer networking equipment from production and user networks.
- Replace end-of-support Tenda 4G06 units with hardware that receives active security maintenance.
# Example iptables rule restricting access to the vulnerable endpoint
iptables -A INPUT -p tcp --dport 80 -m string --string "/goform/DhcpListClient" --algo bm -j DROP
iptables -A INPUT -p tcp --dport 443 -s <trusted-management-subnet> -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
