The PING function on the TP-Link TL-WR840N EU v5 router with firmware through TL-WR840N(EU)_V5_171211 is vulnerable to remote code execution via a crafted payload in an IP address input field.

In TP-Link Wireless N Router WR840N an ARP poisoning attack can cause buffer overflow

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.

A password-disclosure issue in the web interface on certain TP-Link devices allows a remote attacker to get full administrative access to the web panel. This affects WA901ND devices before 3.16.9(201211) beta, and Archer C5, Archer C7, MR3420, MR6400, WA701ND, WA801ND, WDR3500, WDR3600, WE843N, WR1043ND, WR1045ND, WR740N, WR741ND, WR749N, WR802N, WR840N, WR841HP, WR841N, WR842N, WR842ND, WR845N, WR940N, WR941HP, WR945N, WR949N, and WRD4300 devices.

The traceroute function on the TP-Link TL-WR840N v4 router with firmware through 0.9.1 3.16 is vulnerable to remote code execution via a crafted payload in an IP address input field.

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.

The ping feature in the Diagnostic functionality on TP-LINK WR840N v2 Firmware 3.16.9 Build 150701 Rel.51516n devices allows remote attackers to cause a denial of service (HTTP service termination) by modifying the packet size to be higher than the UI limit of 1472.

TP-Link TL-WR840N devices allow remote attackers to cause a denial of service (networking outage) via fragmented packets, as demonstrated by an "nmap -f" command.

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.