Full Disclosure: Re: SSH.com Communications SSH Tectia Authentication Bypass Remote Zeroday Exploit (king cope)

[<Samuel.Lavitt () ssh com>]

High/Critical severity remote authentication bypass in Tectia SSH Server - Workaround

SUMMARY
On Sunday December 2, 2012, a remote authentication bypass vulnerability was disclosed which affects the current 
Unix/Linux versions of Tectia SSH Server. This does not affect client. Windows and zOS servers are not affected. 
Servers that have "old-style" password authentication already disabled are not affected. Password authentication 
through keyboard-interactive authentication is safe.
This vulnerability exploits a bug in the SSH USERAUTH CHANGE REQUEST function. This vulnerability has been confirmed by 
internal testing.
A workaround is to disable "old-style" password authentication on affected versions. The bug only affects “old-style” 
password authentication. Keyboard-interactive, GSSAPI, and public key authentication methods are not affected.

AFFECTED PRODUCTS AND VERSIONS
SSH Tectia Server 6.0.4 to 6.0.20
SSH Tectia Server 6.1.0 to 6.1.12
SSH Tectia Server 6.2.0 to 6.2.5
SSH Tectia Server 6.3.0 to 6.3.2
All products are only the Unix/Linux versions (not Windows or zOS)

CURRENT SITUATION
Effective workaround exists. Updated versions providing a permanent fix to this issue are in testing and are expected 
to be released within the next 24-48 hours.

WORKAROUND
An immediate workaround is to disable “old-style” password authentication by editing the 
/etc/ssh2/ssh-server-config.xml configuration file. Comment out the line (all of them if multiple) containing 
<auth-password /> In XML, comment syntax is <!-- … -->, i.e., change the line to:
<!-- <auth-password /> -->
WE STRONGLY ADVISE MAKING THIS CHANGE IMMEDIATELY, AT LEAST ON ALL EXTERNAL FACING SERVERS.

Note: it is also good to make sure you have keyboard-interactive enabled so that you don't completely prevent password 
authentication, i.e., that the following is in the server configuration file:
<auth-keyboard-interactive>
<submethod-password />
</auth-keyboard-interactive>

SSH Communications Security would like to credit "king cope", isowarez.isowarez.isowarez () googlemail com, with this 
discovery, as that was the first report we received of this issue.
_______________________________________________
Full-Disclosure - We believe in it.
Charter: http://lists.grok.org.uk/full-disclosure-charter.html
Hosted and sponsored by Secunia - http://secunia.com/