Tp-Link TL-WR840N (EU) v6.20 Firmware (0.9.1 4.17 v0001.0 Build 201124 Rel.64328n) is vulnerable to Buffer Overflow via the Password reset feature.

TP-LINK TL-WR840N(ES)_V6.20 was discovered to contain a buffer overflow via the X_TP_ClonedMACAddress parameter.

TP-LINK TL-WR840N(ES)_V6.20 was discovered to contain a buffer overflow via the httpRemotePort parameter.

TP-LINK TL-WR840N(ES)_V6.20 was discovered to contain a buffer overflow via the minAddress parameter.

TP-LINK TL-WR840N(ES)_V6.20 was discovered to contain a buffer overflow via the DNSServers parameter.

oal_ipt_addBridgeIsolationRules on TP-Link TL-WR840N 6_EU_0.9.1_4.16 devices allows OS command injection because a raw string entered from the web interface (an IP address field) is used directly for a call to the system library function (for iptables). NOTE: oal_ipt_addBridgeIsolationRules is not the only function that calls util_execSystem.

TP-Link TL-WR840N v5 00000005 devices allow XSS via the network name. The attacker must log into the router by breaking the password and going to the admin login page by THC-HYDRA to get the network name. With an XSS payload, the network name changed automatically and the internet connection was disconnected. All the users become disconnected from the internet.

TP-Link WR840N devices have a buffer overflow via a long Authorization HTTP header.

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.