An issue was discovered on TP-Link TL-WR840N v5 00000005 0.9.1 3.16 v0001.0 Build 170608 Rel.58696n and TL-WR841N v13 00000013 0.9.1 4.16 v0001.0 Build 170622 Rel.64334n devices. This issue is caused by improper session handling on the /cgi/ folder or a /cgi file. If an attacker sends a header of "Referer: http://192.168.0.1/mainFrame.htm" then no authentication is required for any action.

On TP-Link TL-WR841N v13 00000001 0.9.1 4.16 v0001.0 Build 171019 Rel.55346n devices, all actions in the web interface are affected by bypass of authentication via an HTTP request.

This vulnerability allows remote attackers to execute arbitrary code on affected installations of TP-LINK TL-WR841N routers. Authentication is not required to exploit this vulnerability. The specific flaw exists within the web service, which listens on TCP port 80 by default. When parsing the Host request header, the process does not properly validate the length of user-supplied data prior to copying it to a fixed-length static buffer. An attacker can leverage this vulnerability to execute code in the context of the admin user.

CSRF exists for all actions in the web interface on TP-Link TL-WR841N v13 00000001 0.9.1 4.16 v0001.0 Build 180119 Rel.65243n devices.

The Ping and Traceroute features on TP-Link TL-WR841N v13 00000001 0.9.1 4.16 v0001.0 Build 180119 Rel.65243n devices allow authenticated blind Command Injection.

TP-Link TL-WR841N v13 00000001 0.9.1 4.16 v0001.0 Build 180119 Rel.65243n devices allow clickjacking.