Visit our newest sister site!
Hundreds of free aircraft flight manuals
Civilian • Historical • Military • Declassified • FREE!

TUCoPS :: Unix :: General :: ciaci038.txt

Router Vulnerability



                       The U.S. Department of Energy
                    Computer Incident Advisory Capability
                           ___  __ __    _     ___
                          /       |     /_\   /
                          \___  __|__  /   \  \___

                             INFORMATION BULLETIN

                    Ascend Routing Hardware Vulnerabilities

March 24, 1998 00:00 GMT                                          Number I-038
PROBLEM:       Two vulnerabilities have been identified with the Ascend router.
               1)  UDP packets to the router.
               2)  SNMP "read" and "write" community passwords.
PLATFORM:      Ascend's Pipeline (version 5.0A) and MAX (version 5.0Ap42).
DAMAGE:        1)  If exploited, an attacker could cause the system to lockup,
                   causing denial of service.
               2)  If exploited, an attacker could possibly gain root access
                   if they can guess the community password.
SOLUTION:      1)  Apply workaround.   
               2)  Change the SNMP "read" and "write" community passwords to
                   ones that are difficult to crack.                        
VULNERABILITY  The UDP packet vulnerability has been widely exploited.  The 
ASSESSMENT:    SNMP password vulnerability if exploited, could be very serious.
               Attackers could download the entire configuration of the router.
               With full access to the router, an attacker could use the router
               to "sniff" the network.

[ Start Security Networks Inc. Advisory ]

                       ######    ##   ##    ######
                       ##        ###  ##      ##
                       ######    ## # ##      ##
                           ##    ##  ###      ##
                       ###### .  ##   ## .  ###### .

                           Secure Networks Inc.

                            Security Advisory
                             March 16,  1998

              Security Issues with Ascend Routing Hardware

- ------------------------------------------------------------------------------


Ascend Communications provides several popular routing and access-server
solutions, including the Pipeline access router and the MAX access server.
Due to problems in the Ascend operating system that runs on these
platforms, it is possible to deny service to networks that depend on them.
Additionally, knowledge of the SNMP "write" community (which defaults to
"write") enables an attacker to download the entire configuration file of
the router, which contains access passwords and other sensitive

- ------------------------------------------------------------------------------


Ascend provides a configuration tool for their equipment which enables
operators to reconfigure routers via a graphical interface. This tool is
called the "Ascend Java Configurator". The Ascend Configurator is capable
of locating Ascend routers on a network, using a special probe protocol.

In order to locate Ascend routers, the Configurator broadcasts a specially
formatted UDP packet to the "discard" port (port 9). Ascend routers listen
for these packets and respond with another UDP packet that contains the
symbolic name of the router. In this manner, the Configurator can build
a list of all Ascend routers on the local network.

By sending a specially formatted (but malformed) probe packet to the
discard port of an Ascend router, an attacker can cause an Ascend router
to lock up. Attackers can easily discover Ascend routers to crash by
sending probe packets to the discard port of arbitrary ranges of
addresses; only Ascend routers will respond to them.

- ------------------------------------------------------------------------------


Ascend routers are manageable by the SNMP protocol. Ascend's SNMP support
includes the ability to read and write MIB variables. Ascend's SNMP system
is protected by the SNMP community definitions, which act as passwords for
SNMP access. By default, the SNMP "read" password is "public", and the
SNMP "write" password is "write". An attacker that can guess the SNMP
"read" community can read arbitrary MIB variables, and an attacker that
can guess the "write" community can set arbitrary MIB variables to new

Ascend provides a vendor-specific extension MIB. This MIB includes
variables specific to Ascend equipment. Among these variables is a group
of settings called "sysConfigTftp", which allow the configuration of the
router to be manipulated via the TFTP protocol. By writing to these
variables with SNMP "set" messages, an attacker can download the entire
configuration of the Ascend router.

The full configuration of an Ascend router includes the telnet password
(knowledge of which allows an attacker to gain telnet access to the Ascend
menu interface), all the enhanced access passwords (allowing an attacker
to reconfigure the router from the menu interface), network protocol
authentication keys (including RADIUS and OSPF keys), usernames and
passwords for incoming connections, and usernames, passwords, and dial-up
phone numbers for outgoing connections. All of this information is in

An attacker with full access to an Ascend router can also use it to
"sniff" the networks it is attached to. Ascend routers have an extensive
(and largely undocumented) debugging interface; functions are included in
this interface to obtain hexadecimal dumps of raw Ethernet, ISDN, DS1, and
modem traffic.

- ------------------------------------------------------------------------------


These issues are known to be relevant to Ascend Pipeline and MAX
networking equipment. These vulnerabilities have been confirmed in
Ascend's operating system at version 5.0Ap42 (MAX) and 5.0A (Pipeline).

Ascend's 6.0 operating system disables SNMP "write" access by default.
Previous versions of the software enable SNMP "write" access with a
default community of "write".

- ------------------------------------------------------------------------------


The denial-of-service issue detailed in this advisory is due to an
implementation flaw in Ascend's software. While no immediate fix is
available, it is possible to work around this problem by filtering out
packets to the UDP discard port (9).

Because SNMP "write" access on an Ascend router is equivalent to complete
administrative access, it is very important that the community chosen is
hard to guess. Deployed Ascend equipment should be checked to ensure that
default (or easily guessed) communities are not in use.

The SNMP configuration of an Ascend router is available through the
menuing system, as "Ethernet...Mod Config...SNMP Options...".

- ------------------------------------------------------------------------------


These issues were identified originally by Jennifer Myers and
Thomas H. Ptacek at Secure Networks, Inc. SNI thanks Kit Knox
of CONNECTnet INS, Inc. for his assistance with this work.

Information about Ascend Communications is available at their website
at Products mentioned in this advisory are
trademarks of Ascend.

- ------------------------------------------------------------------------------


Secure Networks, Inc. (SNI) is a security research and development company
based in Calgary, Alberta, Canada. SNI is the largest independent source
of full-disclosure security advisories and new vulnerability information
in the world. For more information about this or other advisories, contact
us at <>. A PGP key is provided if privacy is required.

For the full text of this and all of SNI's other advisories, see our web
page at "". General information about SNI
is available at "".

- ------------------------------------------------------------------------------


he contents of this advisory are Copyright (C) 1998 Secure Networks
Inc, and may be distributed freely provided that no fee is charged for
distribution, and that proper credit is given.

- ------------------------------------------------------------------------------

[ End Security Networks Inc. Advisory ]

CIAC wishes to acknowledge the contributions of Secure Networks Inc. for the
information contained in this bulletin.

CIAC, the Computer Incident Advisory Capability, is the computer
security incident response team for the U.S. Department of Energy
(DOE) and the emergency backup response team for the National
Institutes of Health (NIH). CIAC is located at the Lawrence Livermore
National Laboratory in Livermore, California. CIAC is also a founding
member of FIRST, the Forum of Incident Response and Security Teams, a
global organization established to foster cooperation and coordination
among computer security teams worldwide.

IAC services are available to DOE, DOE contractors, and the NIH. CIAC
can be contacted at:
    Voice:    +1 925-422-8193
    FAX:      +1 925-423-8002
    STU-III:  +1 925-423-2604

For emergencies and off-hour assistance, DOE, DOE contractor sites,
and the NIH may contact CIAC 24-hours a day. During off hours (5PM -
8AM PST), call the CIAC voice number 925-422-8193 and leave a message,
or call 800-759-7243 (800-SKY-PAGE) to send a Sky Page. CIAC has two
Sky Page PIN numbers, the primary PIN number, 8550070, is for the CIAC
duty person, and the secondary PIN number, 8550074 is for the CIAC
Project Leader.

Previous CIAC notices, anti-virus software, and other information are
available from the CIAC Computer Security Archive.

   World Wide Web:
                        (or -- they're the same machine)
   Anonymous FTP:
                        (or -- they're the same machine)
   Modem access:        +1 (925) 423-4753 (28.8K baud)
                        +1 (925) 423-3331 (28.8K baud)

CIAC has several self-subscribing mailing lists for electronic
1. CIAC-BULLETIN for Advisories, highest priority - time critical
   information and Bulletins, important computer security information;
2. SPI-ANNOUNCE for official news about Security Profile Inspector
   (SPI) software updates, new features, distribution and
3. SPI-NOTES, for discussion of problems and solutions regarding the
   use of SPI products.

Our mailing lists are managed by a public domain software package
called Majordomo, which ignores E-mail header subject lines. To
subscribe (add yourself) to one of our mailing lists, send the
following request as the E-mail message body, substituting
ciac-bulletin, spi-announce OR spi-notes for list-name:

E-mail to or
        subscribe list-name
  e.g., subscribe ciac-bulletin

You will receive an acknowledgment email immediately with a confirmation
that you will need to mail back to the addresses above, as per the
instructions in the email.  This is a partial protection to make sure
you are really the one who asked to be signed up for the list in question.

If you include the word 'help' in the body of an email to the above address,
it will also send back an information file on how to subscribe/unsubscribe,
get past issues of CIAC bulletins via email, etc.

PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing
communities receive CIAC bulletins.  If you are not part of these
communities, please contact your agency's response team to report
incidents. Your agency's team will coordinate with CIAC. The Forum of
Incident Response and Security Teams (FIRST) is a world-wide
organization. A list of FIRST member organizations and their
constituencies can be obtained via WWW at

This document was prepared as an account of work sponsored by an
agency of the United States Government. Neither the United States
Government nor the University of California nor any of their
employees, makes any warranty, express or implied, or assumes any
legal liability or responsibility for the accuracy, completeness, or
usefulness of any information, apparatus, product, or process
disclosed, or represents that its use would not infringe privately
owned rights. Reference herein to any specific commercial products,
process, or service by trade name, trademark, manufacturer, or
otherwise, does not necessarily constitute or imply its endorsement,
recommendation or favoring by the United States Government or the
University of California. The views and opinions of authors expressed
herein do not necessarily state or reflect those of the United States
Government or the University of California, and shall not be used for
advertising or product endorsement purposes.

LAST 10 CIAC BULLETINS ISSUED (Previous bulletins available from CIAC)

I-028: Vulnerabilities in CDE
I-029: IBM AIX Telnet Denial-of-Service Vulnerability
I-030: SunOS volrmmount (1) Vulnerability
I-031A: WindowsNT-95 Attacks on DOE Sites
I-032: Sun Solaris Vulnerabilities (vacation, dtaction)
I-033: Sun Solaris Vulnerabilities (ndd, rpc.cmsd)
I-034: Internet Cookies
I-035: SGI Vulnerabilities
I-036: FreeBSD Denial-of Service LAND Attacks
I-037: FreeBSD mmap Vulnerability

Version: 4.0 Business Edition


TUCoPS is optimized to look best in Firefox® on a widescreen monitor (1440x900 or better).
Site design & layout copyright © 1986-2015 AOH