-- John B.
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Preliminary Notice:
Cisco LocalDirector Enable Password Loss
November 16, 1997, 09:00 AM US/Pacific, Revision 2
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This is a preliminary notice describing a security problem about which there
has been customer concern. Cisco does not yet have full information about
this problem. Customers should use great caution in relying on the
information in this notice.
Summary
At least two customers have reported failures in the enable password
mechanism in version 1.6.3 of Cisco's LocalDirector product. Affected
systems allow users to enter privileged mode without providing the correct
enable password; any string will suffice as a password. This applies only to
the privileged-mode enable password; the TELNET access password does not
appear to be affected.
The failure has been reproduced in Cisco's laboratory, but only once.
Unfortunately the problem was reproduced only in the most preliminary stages
of Cisco's investigation. The conditions under which the failure occurs are
not known in detail.
Based on the information presently available, the source of the problem
seems to be that the LocalDirector "forgets" its configured enable password
upon being upgraded to version 1.6.x from an older software version. A
LocalDirector without a configured enable password still does prompt for a
password, even though that password is not checked. This means that the
system's administrator may not notice that the password has been lost for
quite some time, if ever.
Who is Affected
All LocalDirector customers should check to see that their enable passwords
are being enforced properly. Use the "enable" command to enter privileged
mode, and give an invalid password. If the invalid password is accepted, you
are affected.
If the invalid password is not accepted, you are not affected at present...
but bear in mind that we do not yet fully understand the conditions under
which passwords are lost. Until the problem is better understood, we suggest
that all LocalDirector customers, and especially all LocalDirector 1.6.3
customers, take special precautions as outlined in the "Workarounds" section
below.
This problem probably affects all 1.6.x versions of the LocalDirector
software. However, version 1.6.3 is the only 1.6.x version that has been
released to Cisco's general customer base, and Cisco discourages the use of
other 1.6.x versions because of possible software instability.
Because the LocalDirector code is almost entirely separate from the code
used in other Cisco products, it is extremely unlikely that any product
other than the LocalDirector is affected. Classic IOS, as used on Cisco
routers, shares absolutely no password or configuration management code with
the LocalDirector, and is therefore definitely not affected. WANBU and WBU
products, including Catalyst switches and FastPacket switches, are likewise
definitely not affected.
Impact
Any person who can log into an affected LocalDirector via TELNET or over its
its console port can reconfigure or shut down the LocalDirector.
Workarounds
Cisco recommends that customers take the following steps:
1. Consider putting off any software upgrades to version 1.6.3 that may be
scheduled for the week of November 17, 1997, pending new information.
We hope to have better information within a few working days.
2. Check to make sure that enable passwords are being enforced by all
LocalDirectors. If you find that a LocalDirector is not enforcing its
enable password, changing the password using the "enable password"
configuration command should reactivate the password. Remember to save
the new password using the "write memory" command. Recheck password
enforcement after any software upgrade or downgrade.
3. Make sure that you have configured a TELNET access password for your
LocalDirector using the "password" configuration command. If you're not
sure of the secrecy of your TELNET password, consider changing it. If
you allow unprivileged TELNET access by users who should not have
privileged access, consider denying those users access temporarily by
changing the TELNET password.
4. Consider disabling TELNET access altogether, and/or using firewalling
devices to block TELNET access from untrusted hosts, and/or restricting
access from remote hosts using the address-and-mask feature of the
LocalDirector "telnet" configuration command.
5. If you have a dialin modem connected to your LocalDirector's console
port, or if you have the console port connected to a network device
that allows remote access, either disconnect the console or protect it
using the authentication features of the modem or network device to
which it is connected.
Exploitation and Public Announcements
Cisco has had no reports of malicious exploitation of this vulnerability.
This vulernability was first brought to Cisco's attention by a public
announcement on the "bugtraq@netspace.org" mailing list on Thursday,
November 13, 1997. There has been some subsequent discussion on that mailing
list.
Future Work and Updates
Cisco will continue working to characterize this problem and to produce a
software fix. Updated versions of this notice will be posted on Cisco's
Worldwide Web site as more information becomes available. We hope to have
more information by 17:00 US/Pacific time on Monday, November 17, 1997, but
because of the unknown nature of the problem, we can make no guarantees.
Distribution of this Notice
This notice is being sent to the following Internet mailing lists and
newsgroups:
* cisco@spot.colorado.edu
* comp.dcom.sys.cisco
* bugtraq@netspace.org
* first-teams@first.org (includes CERT/CC)
Updates will be sent to some or all of these, as appropriate.
This notice will be posted in the "Field Notices" section of Cisco's
Worldwide Web site, which can be found under "Technical Tips" in the
"Service and Support" section.. The copy on the Worldwide Web will be
updated as appropriate. For this notice only, Web posting is likely to lag
somewhat behind e-mail.
This notice is copyright 1997 by Cisco Systems, Inc. This notice may be
redistributed freely provided that redistributed copies are complete and
unmodified, including all date and version information.
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