D-Link DSL-2760U: cross-site scripting flaw under attack

What is affected

D-Link DSL-2760U is 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.

A cross-site scripting (XSS) vulnerability exists in the D-Link DSL-2760U gateway, allowing remote authenticated users to inject arbitrary web script or HTML.

What an attacker can do

This is a cross-site scripting flaw. It lets an attacker plant a script that runs in the browser of anyone who opens the affected page, which lets them steal that person's session or act on their behalf.

How it is reached

Over the internet or network

Access the attacker needs

A basic user account

Does the victim have to do something?

Yes, the victim must open or click something

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 51% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 99% of all scored vulnerabilities.

Its CVSS severity score is 5.4 out of 10 (medium), as recorded in the US National Vulnerability Database.

Technical description

Multiple cross-site scripting (XSS) vulnerabilities in D-Link DSL-2760U Gateway (Rev. E1) allow remote authenticated users to inject arbitrary web script or HTML via the (1) ntpServer1 parameter to sntpcfg.cgi, username parameter to (2) ddnsmngr.cmd or (3) todmngr.tod, (4) TodUrlAdd parameter to urlfilter.cmd, (5) appName parameter to scprttrg.cmd, (6) fltName in an add action or (7) rmLst parameter in a remove action to scoutflt.cmd, (8) groupName parameter to portmapcfg.cmd, (9) snmpRoCommunity parameter to snmpconfig.cgi, (10) fltName parameter to scinflt.cmd, (11) PolicyName in an add action or (12) rmLst parameter in a remove action to prmngr.cmd, (13) ippName parameter to ippcfg.cmd, (14) smbNetBiosName or (15) smbDirName parameter to samba.cgi, or (16) wlSsid parameter to wlcfg.wl.