CVE-2026-8259: Tenda AC6 Firmware RCE Vulnerability

CVE-2026-8259 Overview

CVE-2026-8259 is an OS command injection vulnerability in the Tenda AC6 wireless router running firmware version 15.03.06.23 on hardware revision 2.0. The flaw resides in the httpd component, specifically in handling of the /goform/telnet endpoint. Attackers can manipulate the lan.ip argument to inject arbitrary operating system commands. The vulnerability is remotely exploitable over the network, and a public disclosure includes exploitation details. The issue is tracked under [CWE-77] (Command Injection) and [CWE-78] (OS Command Injection).

Critical Impact
Authenticated attackers can inject arbitrary OS commands through the lan.ip parameter of the router's telnet configuration endpoint, leading to command execution on the device.

Affected Products

Tenda AC6 hardware revision 2.0
Tenda AC6 firmware version 15.03.06.23
httpd component handling /goform/telnet

Discovery Timeline

2026-05-11 - CVE-2026-8259 published to NVD
2026-05-11 - Last updated in NVD database

Technical Details for CVE-2026-8259

Vulnerability Analysis

The vulnerability resides in the httpd web server bundled with Tenda AC6 firmware 15.03.06.23. The /goform/telnet handler processes the lan.ip parameter without proper sanitization before incorporating it into an operating system command. An attacker submitting a crafted value containing shell metacharacters can break out of the intended command context and execute arbitrary commands on the router. The CWE classifications [CWE-77] and [CWE-78] confirm the root issue is improper neutralization of special elements used in OS commands. Exploitation requires high privileges, which limits the attacker population to users with administrative access to the device interface.

Root Cause

The /goform/telnet endpoint passes the user-supplied lan.ip value into a system shell call without input validation or argument escaping. Shell metacharacters such as ;, |, &, and backticks remain interpretable, allowing command concatenation. The router process runs with elevated privileges typical of embedded Linux services, meaning injected commands execute with broad access to the device filesystem and network stack.

Attack Vector

The attack vector is network-based against the router's web management interface. An authenticated user with high privileges sends a crafted HTTP request to /goform/telnet. The lan.ip parameter carries the injected payload. Exploitation does not require user interaction beyond the attacker's own request. Because the public disclosure on GitHub documents the request structure, weaponization is straightforward for actors who can reach the management interface. See the GitHub Command Injection Report for the technical proof-of-concept.

Detection Methods for CVE-2026-8259

Indicators of Compromise

HTTP POST requests to /goform/telnet containing shell metacharacters such as ;, |, &, or backticks in the lan.ip parameter.
Unexpected telnetd or shell processes spawning from the httpd parent process on the router.
Outbound connections from the router to unfamiliar hosts following administrative HTTP activity.

Detection Strategies

Inspect router HTTP access logs for requests targeting /goform/telnet with non-IP-formatted values in the lan.ip field.
Monitor router-originated network traffic for anomalous outbound connections, reverse shells, or DNS lookups unrelated to normal operation.
Deploy network intrusion detection signatures that flag command-injection patterns in form submissions to Tenda management endpoints.

Monitoring Recommendations

Centralize syslog from network infrastructure devices and alert on configuration endpoint access from non-administrative source addresses.
Track baseline behavior of the AC6 management interface and alert on deviations such as repeated /goform/telnet calls.
Correlate router log activity with endpoint and identity telemetry to identify lateral movement following device compromise.

How to Mitigate CVE-2026-8259

Immediate Actions Required

Restrict access to the Tenda AC6 web management interface to trusted management VLANs or specific administrative hosts only.
Disable remote WAN-side administration if enabled, and rotate administrative credentials to limit privilege abuse.
Audit the device for unauthorized telnet sessions, modified startup scripts, or unexpected listening services.

Patch Information

At the time of publication, no vendor advisory or patch is referenced in the NVD entry. Consult the Tenda Company Website for firmware updates, and review the VulDB Vulnerability Report for tracking status. Where no patch exists, treat the device as end-of-support for security purposes and plan replacement with a vendor-supported platform.

Workarounds

Place the router behind a network segment that blocks untrusted access to TCP ports serving the management interface.
Enforce strong, unique administrator passwords and disable any default accounts to reduce the population of users meeting the privilege requirement.
Disable the telnet configuration feature in the web UI if operational requirements permit.
Replace the affected Tenda AC6 device with a model that receives active firmware updates if no patch is forthcoming.

bash

# Example: restrict access to the router management interface using upstream firewall rules
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -s <admin_subnet> -j ACCEPT
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -j DROP