TP-Link Multiple Archer Devices: file access flaw under attack

What is affected

TP-Link Multiple Archer Devices are the kind of equipment many homes and small offices run for years without touching: a router, camera or storage box. Attackers scan the internet for exposed units, and a hijacked one can spy on traffic or be enrolled in a botnet without any visible sign.

Directory traversal vulnerability in multiple TP-Link Archer devices allows remote attackers to read arbitrary files via a .. (dot dot) in the PATH_INFO to login/.

What an attacker can do

This is a file access flaw. It lets an attacker read or write files they should never reach, such as configuration files that hold passwords, or upload a malicious file that the system then runs.

How it is reached

Over the internet or network

Access the attacker needs

No account needed

Does the victim have to do something?

No, works without the victim doing anything

What to do

1. Check whether you own this device: look at the label on your router, camera or NAS, or open its admin page and note the model and firmware version.
2. Install the latest firmware from the manufacturer's support page or the device's own update menu.
3. If the manufacturer no longer releases updates for the model, replace it. An end-of-life device with an exploited flaw cannot be made safe.
4. Turn off remote administration from the internet unless you truly need it, and change the default admin password.

Apply updates per vendor instructions.

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on March 25, 2022, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by April 15, 2022, a deadline that has already passed. That deadline does not bind anyone else, but it shows how seriously the agency rates it.

The EPSS model estimates a 84% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 99.7% of all scored vulnerabilities.

Its CVSS severity score is 7.5 out of 10 (high), as recorded in the US National Vulnerability Database.

Technical description

Directory traversal vulnerability in TP-LINK Archer C5 (1.2) with firmware before 150317, C7 (2.0) with firmware before 150304, and C8 (1.0) with firmware before 150316, Archer C9 (1.0), TL-WDR3500 (1.0), TL-WDR3600 (1.0), and TL-WDR4300 (1.0) with firmware before 150302, TL-WR740N (5.0) and TL-WR741ND (5.0) with firmware before 150312, and TL-WR841N (9.0), TL-WR841N (10.0), TL-WR841ND (9.0), and TL-WR841ND (10.0) with firmware before 150310 allows remote attackers to read arbitrary files via a .. (dot dot) in the PATH_INFO to login/.