CVE-2026-13516 Overview
CVE-2026-13516 is a stack-based buffer overflow vulnerability in the Tenda JD12L router running firmware version 16.03.53.23. The flaw resides in the fromSetWifiGusetBasic function within the /goform/WifiGuestSet endpoint. Attackers can trigger the overflow by manipulating the shareSpeed argument submitted to the guest Wi-Fi configuration handler. The issue is remotely exploitable over the network and requires only low-level privileges. Public exploit details have been disclosed, increasing the likelihood of opportunistic attacks against exposed devices. The vulnerability is classified under CWE-119 for improper restriction of operations within the bounds of a memory buffer.
Critical Impact
Remote attackers can corrupt stack memory in the router's HTTP configuration service, enabling potential code execution or denial of service against affected Tenda JD12L devices.
Affected Products
- Tenda JD12L router
- Firmware version 16.03.53.23
- /goform/WifiGuestSet HTTP configuration endpoint
Discovery Timeline
- 2026-06-29 - CVE-2026-13516 published to NVD
- 2026-06-29 - Last updated in NVD database
Technical Details for CVE-2026-13516
Vulnerability Analysis
The vulnerability exists in the fromSetWifiGusetBasic function that processes guest Wi-Fi configuration requests submitted to /goform/WifiGuestSet. The function accepts the shareSpeed parameter from HTTP request data and copies it into a fixed-size stack buffer without validating the input length. When an attacker supplies an oversized shareSpeed value, the copy operation writes past the buffer boundary and overwrites adjacent stack memory. This corruption can overwrite saved return addresses and function pointers stored on the stack.
The exploit is publicly available, meaning proof-of-concept payloads are circulating among researchers and threat actors. Successful exploitation can lead to arbitrary code execution on the router's MIPS-based firmware or a crash of the HTTP configuration daemon.
Root Cause
The root cause is missing bounds checking on the shareSpeed argument before it is written to a local stack buffer. Tenda's web configuration handlers historically use unsafe string copy routines such as strcpy or sprintf without validating attacker-controlled input length. This pattern of unchecked input handling in /goform/* endpoints has produced repeated buffer overflow disclosures across the Tenda product line.
Attack Vector
An attacker with access to the router's HTTP administration interface can send a crafted POST request to /goform/WifiGuestSet containing an oversized shareSpeed field. The vulnerability requires low-privilege authentication to reach the vulnerable endpoint. Once the request is processed, the overflow occurs during handling of the fromSetWifiGusetBasic function, corrupting the stack frame. The vulnerability is described in the GitHub Issue Discussion and cataloged in the VulDB CVE Detail entry.
No verified proof-of-concept code is republished here. Refer to the linked public advisories for technical exploitation details.
Detection Methods for CVE-2026-13516
Indicators of Compromise
- HTTP POST requests to /goform/WifiGuestSet containing unusually long shareSpeed parameter values.
- Unexpected reboots or crashes of the Tenda JD12L HTTP daemon following configuration requests.
- Guest Wi-Fi configuration changes originating from unauthorized source addresses.
- Outbound connections from the router to unfamiliar hosts following administrative requests.
Detection Strategies
- Inspect HTTP traffic to the router management interface for requests targeting /goform/WifiGuestSet with parameter lengths exceeding typical values.
- Deploy network intrusion detection signatures that flag oversized POST body fields to Tenda /goform/* endpoints.
- Correlate router log entries showing repeated authentication attempts followed by guest Wi-Fi configuration changes.
Monitoring Recommendations
- Restrict management interface access to trusted administrative VLANs and monitor for unexpected connections.
- Log and alert on any modifications to guest Wi-Fi settings outside of scheduled maintenance windows.
- Track EPSS scoring trends and public exploit availability from the VulDB Vulnerability Overview for updated exploitation likelihood.
How to Mitigate CVE-2026-13516
Immediate Actions Required
- Disable remote management on the Tenda JD12L administration interface and restrict LAN-side access to trusted hosts.
- Change default and low-privilege administrative credentials to strong, unique passwords.
- Disable the guest Wi-Fi feature if it is not required in the deployment.
- Isolate affected routers behind an upstream firewall until vendor patches are available.
Patch Information
At the time of publication, no official vendor patch has been referenced for CVE-2026-13516. Monitor the Tenda Official Website for firmware updates addressing the fromSetWifiGusetBasic buffer overflow. Apply firmware updates immediately once released and verify the fixed version supersedes 16.03.53.23.
Workarounds
- Block external access to TCP ports serving the router's HTTP administration interface using upstream network controls.
- Enforce access control lists that limit /goform/WifiGuestSet requests to a dedicated administrative workstation.
- Consider replacing end-of-support consumer-grade routers with hardware that receives active security maintenance.
# Example: block WAN-side access to the router management interface
iptables -A INPUT -i wan0 -p tcp --dport 80 -j DROP
iptables -A INPUT -i wan0 -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.
