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New claim: D-Link router exposes unprotected config controls to web – DNS hijackers, ahoy!

Zero-day exploit code already published

D-Link router DSL-2740R, and possible more like it, are allegedly vulnerable to DNS hijacking – which hackers can exploit to lure victims to dodgy websites and servers.

According to Bulgarian security researcher Todor Donev, the flaw lies in certain builds of ZyXEL's ZynOS firmware, which is used in network hardware from TP-Link Technologies, ZTE and D-Link. The affected kit is aimed at homes and small businesses.

Routers running the vulnerable software expose their internal web servers to the open internet, Donev claims, and allow anyone to remotely configure the devices without having to log in. An attacker just needs a victim's public IP address – which can be found by scanning the net – and fire off a HTTP request along the lines of:

http://x.x.x.x/Forms/dns_1?Enable_DNSFollowing=1&dnsPrimary=a.a.a.a

It sounds very similar to the vulnerabilities found in ADB Pirelli routers last month.

Donev went public about the D-Link vulnerability without notifying the affected vendors.

By screwing around with a user's DNS settings, it's entirely possible PCs on the network will pick up the new name server IP addresses via DHCP and use them to connect to websites and other systems on the internet. If these name servers are malicious, they could point browsers at websites booby-trapped to infect computers with malware, or bogus login pages to harvest passwords.

Said login pages could be dressed up as a legit webmail or online banking site; if a victim doesn't notice that the site isn't HTTPS protected with the correct certificate, they are going to have a really bad time if they type in their username and password.

Donev has published a proof-of-concept exploit for the D-Link DSL-2740R, a dual-function ADSL modem/wireless router device. This particular device has been discontinued from sale but is still supported.

El Reg asked D-Link to comment on Friday, but we've yet to hear back from the networking firm which, in fairness, seems to have been given no advanced warning of trouble ahead. We will update this story if we learn more. ®

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