TP-Link TL Wr840n Vulnerabilities
22 known CVEs, 6 critical, 1 in CISA's Known Exploited Vulnerabilities catalog. Last updated 2026-10-24.
Known CVEs
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 sessi...
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 sys...
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.
TP-LINK TL-WR840N(ES)_V6.20_180709 was discovered to contain a command injection vulnerability via the component oal_startPing.
TP-LINK TL-WR840N(ES)_V6.20_180709 was discovered to contain a command injection vulnerability via the component oal_setIp6DefaultRoute.
TP-LINK TL-WR840N(ES)_V6.20_180709 was discovered to contain a remote code execution (RCE) vulnerability via the function oal_wan6_setIpAddr.
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-WR841N ated_tp Command Injection Remote Code Execution Vulnerability. This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of TP-Link TL-WR841N routers. A...
TP-Link WR840N devices have a buffer overflow via a long Authorization HTTP header.
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.
Commonly exposed ports
- Port 23 (Telnet) — Sends admin credentials unencrypted — a common target on older router firmware.
- Port 80 (HTTP admin panel) — The web admin UI; dangerous if remote/WAN administration is left enabled.
- Port 7547 (TR-069 (CWMP)) — ISP remote-management protocol — has been the entry point for several router botnets.
- Port 1900 (UPnP/SSDP) — Lets apps on your LAN open firewall holes automatically, sometimes without your knowledge.
Default credentials
From ProbeShield's own tested default-credential list (see probeshield.com/default-passwords/): "admin" / "tplink" or "admin" / "admin123" over HTTP.
Hardening checklist
- Disable remote (WAN-side) administration unless you specifically need it.
- Turn off UPnP unless a specific app you trust requires it.
- Turn off WPS — it can let an attacker bypass your Wi-Fi password.
- Change the default admin username and password to something unique.
- Check for a firmware update in the router’s admin panel and apply it.
- Disable Telnet/SSH management access if you don’t actively use it.
Frequently asked questions
Is my TP-Link TL Wr840n affected by these vulnerabilities? Only if you’re running a firmware version in the affected range listed above and haven’t updated. Check your router's admin panel for its current firmware version and compare it against the ranges below.
How do I update my TP-Link TL Wr840n's firmware? Log into the router's web admin panel (usually at its local IP address) and look for a Firmware Update or System Update section, or use the vendor's mobile app if it has one.
Does ProbeShield fix these vulnerabilities for me? No — ProbeShield scans your network and tells you what it finds (open ports, default credentials, outdated firmware signals) so you know what to fix, and how. It never changes your devices’ settings.
Sources: National Vulnerability Database (NVD), CISA Known Exploited Vulnerabilities Catalog. This page lists which firmware versions are affected — it doesn't claim your specific unit is vulnerable. Check your device's current firmware version in its admin panel and compare it against the ranges above.