DrayTek Vigor Routers: code execution flaw under attack

What is affected

DrayTek Vigor Routers 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.

DrayTek Vigor2960, Vigor300B, and Vigor3900 routers contain an OS command injection vulnerability due to an unknown function of the file /cgi-bin/mainfunction.cgi/apmcfgupload of the component web management interface.

What an attacker can do

This is a code execution flaw. It lets an attacker run their own commands or programs on the affected system. In practice that usually means taking it over: installing malware, stealing data or using it to reach other devices on the same network.

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 mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Vendor advisories and fixes

• fw.draytek.com.twfw.draytek.com.tw/Vigor2960/Firmware/v1.5.1.5/DrayTek_Vigor2960_V1.5.1.5_01release-note.pd
• fw.draytek.com.twfw.draytek.com.tw/Vigor300B/Firmware/v1.5.1.5/DrayTek_Vigor300B_V1.5.1.5_01release-note.pd
• fw.draytek.com.twfw.draytek.com.tw/Vigor3900/Firmware/v1.5.1.5/DrayTek_Vigor3900_V1.5.1.5_01release-note.pd

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on May 15, 2025, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by June 5, 2025, 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 98% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 99.9% of all scored vulnerabilities.

Its CVSS severity score is 6.9 out of 10 (medium), as recorded in the US National Vulnerability Database.

Technical description

A vulnerability, which was classified as critical, was found in DrayTek Vigor2960 and Vigor300B 1.5.1.4. Affected is an unknown function of the file /cgi-bin/mainfunction.cgi/apmcfgupload of the component Web Management Interface. The manipulation of the argument session leads to os command injection. It is possible to launch the attack remotely. The exploit has been disclosed to the public and may be used. Upgrading to version 1.5.1.5 is able to address this issue. It is recommended to upgrade the affected component.