CVE-2025-11386 Overview
CVE-2025-11386 is a stack-based buffer overflow vulnerability in the Tenda AC15 router running firmware version 15.03.05.18. The flaw resides in the /goform/SetDDNSCfg endpoint, where the POST parameter handler fails to validate the length of the ddnsEn argument before copying it into a fixed-size stack buffer. An authenticated attacker on the network can send a crafted HTTP POST request to trigger memory corruption, potentially leading to remote code execution on the device. Public technical details for the issue have been disclosed, increasing the likelihood of exploitation against exposed devices.
Critical Impact
Successful exploitation allows network-adjacent attackers to corrupt router memory and execute arbitrary code, compromising the integrity, confidentiality, and availability of the device and traffic traversing it.
Affected Products
- Tenda AC15 (hardware)
- Tenda AC15 Firmware version 15.03.05.18
- Devices exposing the web management interface (/goform/SetDDNSCfg)
Discovery Timeline
- 2025-10-07 - CVE-2025-11386 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-11386
Vulnerability Analysis
The vulnerability is classified under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer). The Tenda AC15 web server processes HTTP POST requests to the /goform/SetDDNSCfg handler, which configures Dynamic DNS (DDNS) parameters. The handler extracts the ddnsEn parameter from the request body and copies it into a fixed-size buffer on the stack without enforcing length validation.
When an attacker submits an oversized ddnsEn value, the copy operation overruns the buffer boundary and overwrites adjacent stack memory, including saved return addresses. This condition leads to control-flow hijacking on the device. Embedded MIPS or ARM binaries used by the AC15 typically lack modern exploit mitigations such as stack canaries and Address Space Layout Randomization (ASLR), which simplifies reliable exploitation.
Root Cause
The root cause is the absence of bounds checking when handling the ddnsEn POST parameter inside the SetDDNSCfg function. The application trusts attacker-supplied input length and uses an unsafe string copy routine into a stack-allocated buffer.
Attack Vector
Exploitation requires network access to the router's management interface and low-privilege authentication. The attacker sends a crafted HTTP POST request to /goform/SetDDNSCfg containing an oversized ddnsEn parameter. If the management interface is exposed to the WAN, exploitation can occur remotely across the internet. Technical write-up details are available in the GitHub IoT Vulnerability Documentation and the VulDB #327313 Summary.
The vulnerability is described in prose only; no verified proof-of-concept code is reproduced here. Refer to the linked references for the published exploitation details.
Detection Methods for CVE-2025-11386
Indicators of Compromise
- HTTP POST requests to /goform/SetDDNSCfg containing unusually long ddnsEn parameter values
- Unexpected reboots, crashes, or service unavailability of the Tenda AC15 web management daemon
- Outbound connections from the router to unfamiliar command-and-control hosts following configuration changes
- New or modified DDNS configuration entries that were not initiated by an administrator
Detection Strategies
- Inspect web server and router logs for repeated POST requests targeting /goform/SetDDNSCfg from a single source
- Deploy network intrusion detection rules that flag HTTP request bodies where the ddnsEn field exceeds expected lengths
- Correlate router crash events with preceding HTTP traffic to the DDNS configuration endpoint
Monitoring Recommendations
- Restrict and monitor administrative access to the router management interface from internal segments only
- Alert on any WAN-side access attempts to the router's HTTP/HTTPS management port
- Track firmware version inventory to identify devices still running 15.03.05.18
How to Mitigate CVE-2025-11386
Immediate Actions Required
- Disable remote (WAN) management of the Tenda AC15 web interface to limit exposure
- Restrict LAN-side access to the management interface using firewall rules or VLAN segmentation
- Rotate router administrative credentials, since low-privilege authentication is sufficient for exploitation
- Replace affected devices with supported hardware if no vendor patch is available
Patch Information
At the time of publication, no vendor security advisory or patched firmware release was referenced in the available vulnerability data. Administrators should consult the Tenda Official Website for any subsequent firmware updates addressing the SetDDNSCfg handler.
Workarounds
- Block external access to the router's HTTP management port at the perimeter
- Disable the DDNS feature on affected devices if not required
- Place the router behind an upstream firewall that filters POST requests targeting /goform/SetDDNSCfg
# Example perimeter filter to block external access to the AC15 web 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.
