D-Link DIR-859 Router: file access flaw under attack

What is affected

D-Link DIR-859 Router 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.

D-Link DIR-859 routers contain a path traversal vulnerability in the file /hedwig.cgi of the component HTTP POST Request Handler. Manipulation of the argument service with the input ../../../../htdocs/webinc/getcfg/DHCPS6.BRIDGE-1.xml allows for the leakage of session data potentially enabling privilege escalation and unauthorized control of the device. 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.

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 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

• supportannouncement.us.dlink.comsupportannouncement.us.dlink.com/announcement/publication.aspx?name=SAP10371

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on June 25, 2025, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by July 16, 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 83% 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 9.8 out of 10 (critical), as recorded in the US National Vulnerability Database.

Technical description

** UNSUPPORTED WHEN ASSIGNED ** A vulnerability was found in D-Link DIR-859 1.06B01. It has been rated as critical. Affected by this issue is some unknown functionality of the file /hedwig.cgi of the component HTTP POST Request Handler. The manipulation of the argument service with the input ../../../../htdocs/webinc/getcfg/DHCPS6.BRIDGE-1.xml leads to path traversal. The attack may be launched remotely. The exploit has been disclosed to the public and may be used. VDB-251666 is the identifier assigned to this vulnerability. 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.