CVE-2026-3400 Overview
A stack-based buffer overflow vulnerability has been discovered in Tenda AC15 wireless routers running firmware versions up to 15.13.07.13. The vulnerability exists in the /goform/TextEditingConversion file, where improper handling of the wpapsk_crypto2_4g argument allows attackers to trigger a buffer overflow condition. This firmware vulnerability can be exploited remotely over the network, and a public exploit has been released, significantly increasing the risk of active exploitation against vulnerable devices.
Critical Impact
Remote attackers with low-level privileges can exploit this stack-based buffer overflow to potentially achieve code execution on affected Tenda AC15 routers, compromising network infrastructure and enabling lateral movement within target environments.
Affected Products
- Tenda AC15 Firmware (versions up to 15.13.07.13)
- Tenda AC15 Hardware Device
Discovery Timeline
- 2026-03-02 - CVE-2026-3400 published to NVD
- 2026-03-03 - Last updated in NVD database
Technical Details for CVE-2026-3400
Vulnerability Analysis
This vulnerability is classified as a stack-based buffer overflow (CWE-787: Out-of-bounds Write) with an underlying memory boundary issue (CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw resides in the web management interface of the Tenda AC15 router, specifically within the /goform/TextEditingConversion endpoint.
When processing HTTP requests to this endpoint, the firmware fails to properly validate the length of data supplied through the wpapsk_crypto2_4g parameter before copying it to a fixed-size stack buffer. An attacker can craft a malicious request containing an oversized value for this parameter, causing the data to overflow the allocated buffer and overwrite adjacent memory on the stack, including potentially the return address.
The vulnerability is particularly concerning because it can be triggered remotely over the network by any authenticated user with low-level privileges. The public availability of exploit code further increases the immediate risk to organizations running vulnerable firmware versions.
Root Cause
The root cause of this vulnerability is insufficient input validation and improper boundary checking in the Tenda AC15 firmware when handling the wpapsk_crypto2_4g argument in the /goform/TextEditingConversion handler. The firmware uses a fixed-size stack buffer to store user-supplied data without verifying that the input length does not exceed the buffer's capacity. This classic memory safety issue allows attackers to write beyond the buffer boundaries, corrupting stack memory and potentially hijacking program execution flow.
Attack Vector
The attack vector is network-based, requiring an attacker to send specially crafted HTTP requests to the router's web management interface. The attacker must have low-level authentication privileges to access the vulnerable endpoint. Once authenticated, the attacker can submit a malicious POST request to /goform/TextEditingConversion with an oversized wpapsk_crypto2_4g parameter value designed to overflow the stack buffer.
The exploitation mechanism involves overwriting the saved return address on the stack with a controlled value, allowing the attacker to redirect execution to attacker-controlled code or existing gadgets within the firmware. Successful exploitation could result in arbitrary code execution with the privileges of the web server process, typically running as root on embedded devices like the Tenda AC15.
For detailed technical analysis and proof-of-concept information, refer to the Yuque Document Analysis and VulDB Entry #348295.
Detection Methods for CVE-2026-3400
Indicators of Compromise
- Unusual HTTP POST requests to /goform/TextEditingConversion endpoint containing abnormally long parameter values
- Web server crashes or unexpected reboots of Tenda AC15 routers
- Presence of unauthorized processes or connections originating from the router
- Modified firmware configuration or unexplained changes to router settings
Detection Strategies
- Monitor network traffic for HTTP requests to /goform/TextEditingConversion with payload sizes exceeding normal operational parameters
- Implement web application firewall (WAF) rules to detect and block requests containing oversized wpapsk_crypto2_4g parameter values
- Deploy network intrusion detection signatures targeting buffer overflow exploitation patterns in HTTP POST bodies
- Enable logging on network devices to capture and analyze traffic destined for router management interfaces
Monitoring Recommendations
- Establish baseline network behavior for router management traffic and alert on anomalies
- Configure centralized logging for all Tenda AC15 devices to capture web server access logs
- Implement network segmentation to isolate router management interfaces from general network traffic
- Regularly audit router configurations and firmware versions across the organization
How to Mitigate CVE-2026-3400
Immediate Actions Required
- Identify all Tenda AC15 routers in your environment running firmware versions up to 15.13.07.13
- Restrict access to the web management interface by implementing network-level access controls
- Disable remote management features if not strictly required for operations
- Monitor for firmware updates from Tenda and apply patches as soon as they become available
Patch Information
At the time of publication, no official patch has been confirmed by the vendor. Organizations should monitor the Tenda Official Website for security advisories and firmware updates addressing this vulnerability. Given the public availability of exploit information, prioritize alternative mitigations until an official fix is released.
Additional vulnerability details can be found at:
Workarounds
- Implement strict access control lists (ACLs) to limit access to the router's web management interface to trusted IP addresses only
- Place the router management interface on a dedicated management VLAN inaccessible from untrusted networks
- Use a VPN for remote administration instead of exposing the web interface directly
- Consider replacing affected devices with alternative hardware if patching is not available in a timely manner
# Network access control example (firewall rule to restrict management access)
# Allow management access only from trusted administrator subnet
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
