CVE-2026-5155: Tenda CH22 Firmware Buffer Overflow Flaw

CVE-2026-5155 Overview

CVE-2026-5155 is a stack-based buffer overflow vulnerability in the Tenda CH22 router running firmware version 1.0.0.1. The flaw resides in the fromAdvSetWan function within the /goform/AdvSetWan endpoint, which is part of the device's Parameter Handler component. Attackers can trigger the overflow by manipulating the wanmode argument supplied to the handler. The vulnerability is remotely exploitable over the network and a public exploit description has been disclosed. The weakness is classified under CWE-119 and CWE-787, reflecting improper restriction of operations within memory bounds and an out-of-bounds write.

Critical Impact
Remote attackers with low privileges can corrupt stack memory on Tenda CH22 routers, potentially achieving arbitrary code execution and full device compromise.

Affected Products

Tenda CH22 hardware device
Tenda CH22 firmware version 1.0.0.1
/goform/AdvSetWan Parameter Handler component

Discovery Timeline

2026-03-30 - CVE-2026-5155 published to NVD
2026-04-02 - Last updated in NVD database

Technical Details for CVE-2026-5155

Vulnerability Analysis

The vulnerability exists in the fromAdvSetWan function exposed through the /goform/AdvSetWan HTTP endpoint on the Tenda CH22 web management interface. This handler parses user-supplied parameters from advanced WAN configuration requests. When the wanmode parameter is processed, the function copies attacker-controlled data into a fixed-size stack buffer without enforcing length validation. An oversized wanmode value overflows the buffer and overwrites adjacent stack data, including saved return addresses.

This flaw allows remote attackers to corrupt control-flow data structures. Successful exploitation can lead to denial of service through process crash or arbitrary code execution under the privileges of the web management daemon, which typically runs as root on consumer routers.

Root Cause

The root cause is the absence of bounds checking when handling the wanmode HTTP parameter inside fromAdvSetWan. The function relies on unsafe string copy operations against a stack-allocated buffer of insufficient size. This pattern is consistent with CWE-787 (Out-of-bounds Write) where untrusted input directly drives memory write operations.

Attack Vector

An attacker reaches the vulnerable endpoint over the network by sending a crafted HTTP request to /goform/AdvSetWan with an oversized wanmode parameter. Exploitation requires authenticated access to the management interface, but credentials are often weak, default, or shared across deployments. If the management interface is exposed to the WAN, the attack surface expands to internet-based adversaries.

No verified proof-of-concept code is published in this CVE record. Technical details have been documented in the GitHub Vulnerability Report and the VulDB Vulnerability #354187 entry.

Detection Methods for CVE-2026-5155

Indicators of Compromise

HTTP POST requests to /goform/AdvSetWan containing abnormally long wanmode parameter values.
Unexpected reboots, watchdog resets, or httpd process crashes on Tenda CH22 devices.
Outbound connections from the router to unfamiliar hosts following management interface activity.

Detection Strategies

Inspect web server and router system logs for malformed or oversized requests targeting /goform/AdvSetWan.
Deploy network IDS signatures that flag HTTP requests where wanmode exceeds expected configuration values.
Monitor for repeated authentication attempts followed by configuration endpoint access from a single source.

Monitoring Recommendations

Capture and retain HTTP request logs from router management interfaces for retrospective analysis.
Alert on management interface access from non-administrative network segments or external IP ranges.
Track firmware version inventories to identify CH22 devices running 1.0.0.1 that require remediation.

How to Mitigate CVE-2026-5155

Immediate Actions Required

Restrict access to the /goform/AdvSetWan endpoint and the broader web management interface to trusted administrative networks only.
Disable remote WAN-side management on all Tenda CH22 routers until a patched firmware is available.
Rotate administrative credentials and enforce strong, unique passwords on every device.

Patch Information

At the time of publication, no vendor advisory or fixed firmware build has been listed in the Tenda Company Homepage references for CVE-2026-5155. Administrators should monitor Tenda's support channels for an updated firmware release addressing the fromAdvSetWan overflow and apply it as soon as it becomes available.

Workarounds

Place affected routers behind a network segmentation boundary that blocks untrusted hosts from reaching the management interface.
Use access control lists or host firewall rules to restrict TCP access to the router's HTTP/HTTPS administration ports.
Where feasible, replace end-of-support Tenda CH22 hardware with actively maintained equipment supporting current security updates.

bash

# Configuration example: restrict router management access to a trusted subnet
iptables -A INPUT -p tcp --dport 80 -s 10.10.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 10.10.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP