Hi Terry,
On Thu, Jan 24, 2008 at 03:42:53AM -0000, tbbunn@ctc.net wrote:
Back in May of last year I started doing research on any possible
security flaws that exist in the Pix/ASA Finesse operating System,
versions 7.1 and 7.2. I discovered that a design flaw that was
previously unknown in Finesse will allow a level 0 user to escalate
their privilege to level 15. I believe the vulnerability may originate
in the local authentication service, thus not being possible to
exploit when Radius and TACACS is implemented. Implementing AAA in any
other way that keeps the passwords locally defined seems to have no
affect on the vulnerability. I have been able to repeatedly bypass the
privilege-exec login both locally, through the console and remotely,
through a telnet connection. After many attempts I have found that the
SSH service does not seem to suffer from the vulnerability.
I am now going to go over the simplicity of the exploit and I will be
releasing a white paper hopefully sooner than later on the specifics
of the underlying cause. Once a user has logged on to the user-exec
(level0) of the device they will then be able to proceed with the
<enable> command which should give you a login prompt. At this prompt
if you move your cursor forward with a space or character(it doesn't
matter if there are more then one), and then proceed to delete any
spaces or characters, by holding down the backspace a second after
deleting the last character it should immediately drop you into level
15 privilege-exec mode. This attack was originally performed on a PIX
515E running version 7.2 of Finesse. I will be posting all updates
regarding this exploit as they come, and I apologize for it taking so
long to release this information.
Dumb question: can you reproduce this issue when you have a non-blank
enable password? I can see this behavior when a blank enable password is
set, but if I have a non-blank enable password I don't see the behavior
- I get dropped back into unprivilege EXEC after using the backspace
key.
When the enable password is blank you still get prompted for a password
when you want to go into privileged EXEC mode via the "enable" command.
However, hitting just <Enter> will grant you access. There is no
password set after all.
Could you make sure that you have an non-blank enable password set by
using the command "enable password <some password>" and try again?
Note: even if "show running-config enable" shows an "enable password"
command in the configuration that doesn't mean that the enable password
is non-blank; the output just displays a hash of a blank password.
Cheers,
--
Eloy Paris.-
CCIE #19207
Product Security Incident Response Team (PSIRT)
Cisco Systems, Inc.
