D-Link Router Vulnerable To Authentication Bypass

Multiple D-Link, Planex and Virgin Mobile routers have a firmware vulnerability that attackers could exploit to directly access and alter the devices.

Multiple D-Link routers are vulnerable to a simple exploit that would allow an attacker to gain direct access to the device without first having to authenticate.
That warning came in a Saturday
post to embedded device hacking blog /dev/ttyS0
written by
Craig Heffner
, a vulnerability researcher with Tactical Network Solutions.
On a whim I downloaded firmware v1.13 for the DIR-100 revA, Heffner said, referring to a widely used version of D-Links router firmware. After using a firmware analysis tool known as
Binwalk
, soon I had the firmwares Web server (/bin/webs) loaded into IDA, he added, referring to an interactive disassembler -- IDA -- which is used to reverse-engineer code.
Perusing the code, Heffner found a variable called alpha_auth_check -- the alpha apparently refers to
D-Link spinoff Alpha Networks
, while auth means authentication -- that returns a value of 1 if the user has been authenticated. After a bit of exploratory work, Heffner found that if he changed a browsers
HTTP user-agent string
to xmlset_roodkcableoj28840ybtide then you can access the Web interface without any authentication and view/change the device settings.
[ Dont be a victim. See
15 Signs Pointing To A Data Breach
. ]
Heffner doesnt appear to be the first person to have recovered this string from inside the D-Link firmware. A quick Google for the xmlset_roodkcableoj28840ybtide string turns up only a single Russian forum post from a few years ago, which notes that this is an interesting line inside the /bin/webs binary, he said. Id have to agree.
A spokesman for D-Link didnt immediately respond to an emailed query about whether it had verified the vulnerability detailed by Heffner, and if so, how the company planned to notify and issue updates to consumers who own a vulnerable device.
Based on a search made with the
embedded Web server search engine Shodan
, the vulnerable firmware appears to be used by at least seven routers sold by D-Link (DIR-100, DI-524, DI-524UP, DI-604S, DI-604UP, DI-604+, TM-G5240) as well as two Planex routers (BRL-04UR, BRL-04CW), according to Heffner. Several people have reported ... that some versions of the DIR-615 are also affected, including those distributed by Virgin Mobile, he said in a later update to his blog post. I have not yet verified this, but it seems quite reasonable.
Whats the count of the total number of networked D-Link devices that are affected by the vulnerability? That remains to be seen, although Robert David Graham, CEO of Errata Security,
said Monday
that he was scanning the entire Internet for the D-Link xmlset_roodkcableoj28840ybtide backdoor using his Masscan tool, which can be used to
scan the Internet
for certain variables, which in this case would be fingerprints of the vulnerable firmware. Graham said he hoped to be able to report on the results of his scan by Monday afternoon.
Whats the risk from an attacker gaining full access to a router? For starters, the attacker could eavesdrop on the network by loading the router with custom firmware designed to
send a copy of all data
flowing to or from the device to an attacker-controlled server. Likewise, the router could be configured to automatically launch distributed denial-of-service attacks against designated sites.
As Heffners facility with reverse-engineering device firmware suggests, this isnt his first foray into hacking networking equipment. At this past summers Black Hat conference in Las Vegas, for example, the researcher highlighted how consumer-grade as well as enterprise-class networked surveillance cameras from the likes of D-Link, Trendnet, Cisco, IQInvision, Alinking and 3SVision were
vulnerable to zero-day flaws
that would allow an attacker to freeze or modify their video streams. That research was the latest in a long line of
vulnerability reports
involving Internet protocol (IP) cameras.

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D-Link Router Vulnerable To Authentication Bypass