D-Link Multiple NAS Devices: authentication bypass flaw under attack

What is affected

D-Link Multiple NAS 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.

D-Link DNS-320L, DNS-325, DNS-327L, and DNS-340L contains a hard-coded credential that allows an attacker to conduct authenticated command injection, leading to remote, unauthorized code execution.

What an attacker can do

This is a authentication bypass flaw. It lets an attacker get in without a valid username and password and act as a legitimate user, often as an administrator.

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.

This vulnerability affects legacy D-Link products. All associated hardware revisions have reached their end-of-life (EOL) or end-of-service (EOS) life cycle and should be retired and replaced per vendor instructions.

Vendor advisories and fixes

• supportannouncement.us.dlink.comsupportannouncement.us.dlink.com/security/publication.aspx?name=SAP10383

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on April 11, 2024, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by May 2, 2024, 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 9.8 out of 10 (critical), as recorded in the US National Vulnerability Database.

Technical description

** UNSUPPORTED WHEN ASSIGNED ** A vulnerability, which was classified as very critical, has been found in D-Link DNS-320L, DNS-325, DNS-327L and DNS-340L up to 20240403. This issue affects some unknown processing of the file /cgi-bin/nas_sharing.cgi of the component HTTP GET Request Handler. The manipulation of the argument user with the input messagebus leads to hard-coded credentials. The attack may be initiated remotely. The exploit has been disclosed to the public and may be used. The associated identifier of this vulnerability is VDB-259283. NOTE: This vulnerability only affects products that are no longer supported by the maintainer. NOTE: Vendor was contacted early and confirmed immediately that the product is end-of-life. It should be retired and replaced.