CVE-2026-11410: TL-WR940N v6 RCE Vulnerability

CVE-2026-11410 Overview

CVE-2026-11410 is an authenticated operating system (OS) command injection vulnerability in the TP-Link TL-WR940N v6 router. The flaw resides in the BigPond Cable (BPA) Wide Area Network (WAN) configuration module. The module fails to sanitize user-supplied input before passing it to system shell routines.

An attacker with administrative credentials on an adjacent network can inject arbitrary shell commands. The router executes those commands with elevated privileges, granting full control over the device. The vulnerability is tracked under CWE-78, Improper Neutralization of Special Elements used in an OS Command.

Critical Impact
An authenticated adjacent-network attacker can execute arbitrary OS commands as a privileged user, leading to full router compromise, traffic interception, and pivot opportunities into the connected LAN.

Affected Products

TP-Link TL-WR940N hardware revision v6
BigPond Cable (BPA) WAN configuration module on affected firmware
Deployments exposing the router admin interface to adjacent network clients

Discovery Timeline

2026-06-17 - CVE-2026-11410 published to the National Vulnerability Database (NVD)
2026-06-18 - Last updated in NVD database

Technical Details for CVE-2026-11410

Vulnerability Analysis

The TL-WR940N v6 web administration interface exposes the BigPond Cable connection type as a selectable WAN protocol. When an administrator submits BPA configuration parameters, the firmware concatenates those values into shell command strings without escaping or filtering metacharacters.

An attacker who is already authenticated to the admin panel can supply payloads containing shell separators such as ;, |, &&, or backticks. The router invokes the underlying BusyBox shell, which interprets the injected tokens as additional commands. Because the web service runs with root-equivalent privileges on embedded Linux, injected commands inherit those privileges.

The attack requires high privileges (administrative login) and adjacent network access, which limits exposure to attackers on the same Layer 2 segment or those who can chain it with credential theft, default-credential reuse, or cross-site request forgery (CSRF).

Root Cause

The root cause is improper neutralization of special elements in OS commands [CWE-78]. The BPA WAN handler accepts string fields from the HTTP POST body and inserts them directly into a shell invocation. No allowlist validation, character escaping, or use of execve-style argument arrays is performed.

Attack Vector

Exploitation proceeds in three stages. First, the attacker authenticates to the TL-WR940N web interface using valid administrator credentials. Second, the attacker navigates to the WAN settings page and selects the BigPond Cable connection type. Third, the attacker submits a configuration request where a BPA parameter (for example the server hostname or username field) contains a shell metacharacter followed by an arbitrary command.

The injected command executes synchronously inside the router. Typical post-exploitation actions include enabling telnet, dropping a reverse shell to an attacker-controlled host, modifying DNS resolvers to intercept LAN traffic, or persisting malicious scripts in writable flash partitions. See the TP-Link TL-WR940N firmware download page for the affected product family.

Detection Methods for CVE-2026-11410

Indicators of Compromise

Unexpected outbound connections originating from the router management IP to unknown hosts
Changes to DNS server entries, static routes, or firewall rules in router configuration backups without a change-management record
Presence of new processes such as telnetd, nc, or shell interpreters listening on non-standard ports
Administrative login events from adjacent-network MAC or IP addresses that do not match approved operator workstations

Detection Strategies

Inspect HTTP POST bodies sent to the WAN configuration endpoint for shell metacharacters such as ;, |, &, $(), and backticks in BPA-related parameters
Compare running firmware checksums and configuration exports against a known-good baseline taken immediately after patching
Alert on any router administrative session that is followed by configuration writes to WAN settings outside scheduled maintenance windows

Monitoring Recommendations

Forward router syslog and authentication events to a centralized logging platform for retention and correlation
Monitor adjacent-network segments for ARP, DHCP, and DNS anomalies that may indicate a compromised gateway
Review administrator account usage and enforce session timeouts on the device web interface

How to Mitigate CVE-2026-11410

Immediate Actions Required

Apply the latest firmware available from the TP-Link TL-WR940N v6 firmware page once a fixed build is published
Rotate the router administrator password and disable any default or shared credentials
Restrict access to the management interface so that only trusted, wired LAN hosts can reach it
Disable the BigPond Cable (BPA) WAN connection type if it is not required for the deployment

Patch Information

TP-Link maintains firmware downloads and product lifecycle guidance on its support portal. Refer to the TP-Link TL-WR940N v6 firmware page for the latest release notes and to the TP-Link FAQ for TL-WR940N for upgrade instructions. If the device is end-of-life, plan migration to a currently supported model.

Workarounds

Disable remote management and bind the web administration interface to the LAN only
Place the router behind a separate management VLAN with access control lists (ACLs) limiting which hosts may reach TCP/80 and TCP/443
Use a non-BPA WAN connection type (PPPoE, Dynamic IP, or Static IP) where the ISP permits, removing the vulnerable code path from active use
Enforce multi-factor controls at the network perimeter to reduce the risk of credential reuse against the device

bash

# Example: restrict router admin interface to a single management host using upstream firewall ACL
# Replace 192.0.2.10 with the trusted administrator workstation
# Replace 192.168.0.1 with the router LAN IP
iptables -A FORWARD -s 192.0.2.10 -d 192.168.0.1 -p tcp --dport 80 -j ACCEPT
iptables -A FORWARD -d 192.168.0.1 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 192.168.0.1 -p tcp --dport 443 -j DROP