Dangerous bug in TP-Link Archer router - Upgrade immediately

A dangerous bag was found on TP-Link's Archer router, which allows for unauthorized access with no password and with administrator privileges. Anyone who owns such a router should upgrade their device immediately.

TP-Link has a critical vulnerability in some of their models Archer routers, which could allow intruders to cancel administrator passwords and gain remote control of devices via LAN and Telnet connection.

According to researcher Grzegorz Wypych of IBM X-Force Red, if the attackers send an HTTP request to these routers containing a string of characters greater than the allowed number of bytes, the result will be the user password being completely canceled and replaced with a blank value.

This works despite the built-in validation because it only checks the referent's HTTP headers, allowing the attacker to deceive the router's httpd service, and to recognize the request as valid using the hardcoded value tplinkwifi.net.

Since the only type of users on these routers is the administrator with full root privileges, once the intruders bypass the authentication process, they will automatically receive administrator privileges on the router.

Accordingly, the legitimate user will be locked out and will no longer be able to connect to the router with their passwords. The scenario gets even worse, since even if the router's owner manages with a hardreset and sets a new password on the device, the attackers could again cancel another LAN request.

This defect is considered critical as it may grant unauthorized third party access to the router with administrator privileges. The risk is of course greater in business networks, where routers such as these are used to give Wi-Fi access to guests.

Security fixes available
TP-Link has already released updates to help customers protect their routers from attacks that could abuse this security vulnerability, called CVE-2019-7405.

You can download the security updates for Archer C5 V4, Archer MR200v4, Archer MR6400v4, and Archer MR400v3 routers from the table below.