Monday, February 12, 2007

0day in Solaris 10 and 11 Telnet

From SANS: Another good reason to stop using telnet

Published: 2007-02-11,
Last Updated: 2007-02-11 23:07:07 UTC
by donald smith (Version: 1)

There is a major zero day bug announced in solaris 10 and 11 with the telnet and login combination.
It has been verified. In my opinion NOBODY be should running telnet open to the internet.

The issue:
The telnet daemon passes switches directly to the login process which looks for a switch that allows root to login to any account without a password. If your telnet daemon is running as root it allows unauthenticated remote logins.

Telnet should be disabled. Since 1994 the cert.org team has recommended using something other then plain text authentication due to potential network monitoring attacks. http://www.cert.org/advisories/CA-1994-01.html
“We recognize that the only effective long-term solution to prevent these attacks is by not transmitting reusable clear-text passwords on the network.“

If remote shell access is required ssh is a better choice then telnet. We have done articles about securing ssh in the past. http://isc.sans.org/diary.html?storyid=1541

The FIX:
To disable telnet in solaris 10 or 11 this command should work.
svcadm disable telnet

The Mitigations:
Limit your exposure if you must run telnet on your solaris system it is recommend that you use firewall(s) to limit what IP can connect to your telnet services.

Another mitigation that works is this:
inetadm -m svc:/network/telnet:default exec="/usr/sbin/in.telnetd -a user"

I am not going to include the site with the exploit. No special tools are required to exploit this vulnerability.

Thanks to Chris and Thomas who notified us of this issue and all the fellow handlers that helped verify, mitigate and review this report.

From SecuriTeam: Solaris Telnet 0day or Embarrassment

Johannes Ullrich from the SANS ISC sent this to me and then I saw it on the DSHIELD list:

If you run Solaris, please check if you got telnet enabled NOW. If you
can, block port 23 at your perimeter. There is a fairly trivial Solaris
telnet 0-day.

telnet -l “-froot” [hostname]

will give you root on many Solaris systems with default installs
We are still testing. Please use our contact form at
https://isc.sans.org/contact.html
if you have any details about the use of this exploit.

You mean they still use telnet?!

Gadi Evron,
ge@linuxbox.org.