CVE-2026-15696 Overview
CVE-2026-15696 is a stack-based buffer overflow in the Tenda BE12 Pro router firmware version 16.03.66.23. The flaw resides in the fromVirtualSer function handling requests to the /goform/VirtualSer endpoint. An attacker can manipulate the page argument to overflow a fixed-size stack buffer. The vulnerability is exploitable over the network and public exploit details have been disclosed. The weakness maps to [CWE-119], improper restriction of operations within the bounds of a memory buffer.
Critical Impact
Remote attackers with low privileges can trigger memory corruption on affected Tenda BE12 Pro devices, potentially leading to arbitrary code execution or device crash.
Affected Products
- Tenda BE12 Pro firmware version 16.03.66.23
- /goform/VirtualSer web management endpoint
- fromVirtualSer request handler function
Discovery Timeline
- 2026-07-14 - CVE-2026-15696 published to NVD
- 2026-07-14 - Last updated in NVD database
Technical Details for CVE-2026-15696
Vulnerability Analysis
The vulnerability exists in the fromVirtualSer function that processes HTTP requests to the /goform/VirtualSer handler on the router's web management interface. The function reads the page parameter from the incoming request and copies its contents into a fixed-size stack buffer without validating the input length. Because the copy operation lacks bounds checking, an oversized page value overwrites adjacent stack memory, including saved return addresses and function pointers. Successful exploitation allows attackers to hijack control flow of the HTTP server process, which typically runs with elevated privileges on embedded routers. The exploit has been disclosed publicly, increasing the likelihood of active exploitation against exposed devices.
Root Cause
The root cause is unchecked user-controlled input flowing into a stack buffer copy operation inside fromVirtualSer. The handler trusts the length of the page argument supplied through the web request without applying strncpy, snprintf, or comparable length-limited string operations. This is a classic instance of [CWE-119], where the code fails to restrict operations to the intended buffer bounds.
Attack Vector
Exploitation requires network access to the router's web administration interface and low-privilege authenticated access. An attacker sends a crafted HTTP request to /goform/VirtualSer with an overlong page parameter. The attack complexity is low and no user interaction is required. Devices exposing the management interface to untrusted networks are at highest risk. The EPSS score is 0.796% with a percentile of 52.4, reflecting moderate short-term exploitation likelihood given the public disclosure.
No verified proof-of-concept code has been reviewed by SentinelLabs. Technical details are referenced in the GitHub Issue Discussion and VulDB Vulnerability Overview.
Detection Methods for CVE-2026-15696
Indicators of Compromise
- HTTP POST or GET requests to /goform/VirtualSer containing unusually long page parameter values.
- Web server or httpd process crashes and unexpected restarts on Tenda BE12 Pro devices.
- Outbound connections from the router to unfamiliar hosts following a suspicious management request.
- Configuration changes or new port-forwarding rules created outside of normal administrative activity.
Detection Strategies
- Inspect network traffic for HTTP requests targeting /goform/VirtualSer with parameter lengths exceeding typical form input sizes.
- Deploy IDS or IPS signatures matching oversized page= values directed at Tenda administrative endpoints.
- Correlate router syslog entries showing httpd restarts with preceding inbound requests to the management interface.
Monitoring Recommendations
- Forward router logs to a centralized log platform and alert on repeated crashes of the web management service.
- Monitor for authentication events on the router administration interface originating from non-management network segments.
- Track outbound traffic from router IPs to detect post-exploitation command-and-control behavior.
How to Mitigate CVE-2026-15696
Immediate Actions Required
- Restrict access to the router web management interface to trusted internal management VLANs only.
- Disable remote WAN-side administration on Tenda BE12 Pro devices until a vendor patch is available.
- Rotate router administrator credentials and enforce strong, unique passwords to limit low-privilege abuse paths.
- Audit port-forwarding and virtual server configurations for unauthorized entries.
Patch Information
At the time of publication, no vendor patch has been referenced in the NVD entry. Monitor the Tenda Official Website and the VulDB CVE Report for firmware updates addressing fromVirtualSer. Apply firmware updates immediately upon release.
Workarounds
- Place affected routers behind an upstream firewall that blocks external access to the web administration interface.
- Use ACLs on the router to permit administrative HTTP requests only from specific management IP addresses.
- Segment the router management plane from user and IoT networks to reduce the attack surface for low-privileged attackers.
- Replace end-of-support or unpatched devices with hardware receiving active security maintenance.
# Example: block external access to Tenda web admin at upstream firewall (iptables)
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -m iprange ! --src-range 10.0.0.10-10.0.0.20 -j DROP
iptables -A FORWARD -p tcp -d <router_ip> --dport 443 -m iprange ! --src-range 10.0.0.10-10.0.0.20 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
