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AUSCERT External Security Bulletin Redistribution
ESB-2001.281 -- Cisco Security Advisory
VPN 3000 Concentrator IP Options Vulnerability
12 July 2001
AusCERT Security Bulletin Summary
Product: Cisco VPN 3000 series concentrators
Vendor: Cisco Systems
Operating System: Releases prior to 2.5.2 (F)
Impact: Denial of Service
Access Required: Remote
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Cisco Security Advisory: VPN 3000 Concentrator IP Options Vulnerability
For Public Release 2001 April 12 at 1500 UTC
If a crafted IP packet, with an invalid IP Option setting is transmitted to
a VPN 3000 series concentrator on the same network segment (no routers in
between), it can cause the VPN 3000 series concentrator to hang with a 100%
CPU Utilization. The concentrator would then have to be reset. After
rebooting, the equipment would function normally until the crafted IP
packet is received again. The defect can be exploited to produce a denial
of service (DoS) attack.
The vulnerability is described in Cisco bug id CSCds92460.
This notice will be posted at
Cisco VPN 3000 series concentrators running software releases up to but not
including revision 2.5.2 (F) are affected by this vulnerability. This
series includes models 3005, 3015, 3030, 3060, and 3080.
Any VPN 3000 series concentrators running revision 2.5.2 (F) or later are
unaffected by this vulnerability.
This vulnerability does not affect the VPN 5000 series concentrators. No
other Cisco product is known to be affected by this vulnerability.
To determine if a Cisco VPN 3000 series concentrator is running affected
software, check the revision via the web interface or the console menu.
If a crafted IP packet, with an invalid IP Option setting, is transmitted
to a VPN 3000 series concentrator on the same network segment (no routers
in between), on either the Inside or the Outside interface, it can cause
the VPN 3000 series concentrator to hang with a 100 % CPU Utilization. The
concentrator would then have to be reset via the console port as no SNMP or
HTTP remote management control would be possible. After rebooting, the
equipment would function normally until the crafted IP packet is received
In order to exploit this vulnerability the attacker must be on the same
network segment as the concentrator without any routers in between. A
crafted IP packet traversing a router would typically get its invalid IP
Options dropped and would not be able to affect the VPN 3000 series
The vulnerability is documented as Cisco bug id CSCds92460.
When this crafted IP packet is received by the VPN 3000 series
concentrator, the concentrator will stop passing traffic and will not
respond to any management inquiries via SNMP, Telnet or HTTP. However
management via the console port is possible.
For VPN 3000 series concentrator models 3015, 3030, 3060, and 3080 the CPU
Utilization bar graph indicator on the front panel will go to 100%.
Software Versions and Fixes
The vulnerability has been fixed in revision 2.5.2 (E) code. The fix will
be carried forward into all future releases.
However due to the advisory at
recommended revision to upgrade to is 2.5.2 (F)
Upgrade can be done via the remote software upgrade feature using the VPN
3000 series concentrator's web based management interface.
Obtaining Fixed Software
Cisco is offering free software upgrades to remedy this vulnerability for
all affected customers. Customers with service contracts may upgrade to any
software release. Customers may install only the feature sets they have
Fixed software is currently available.
Customers with contracts should obtain upgraded software through their
regular update channels. For most customers, this means that upgrades
should be obtained via Cisco's Software Center at http://www.cisco.com/.
Customers without contracts or warranty should get their upgrades by
contacting the Cisco Technical Assistance Center (TAC) as shown below:
* (800) 553-2447 (toll-free in North America)
* +1 408 526 7209 (toll call from anywhere in the world)
* e-mail: firstname.lastname@example.org
See http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml for
additional TAC contact information, including instructions and e-mail
addresses for use in various languages.
Give the URL of this notice as evidence of your entitlement to a free
upgrade. Free upgrades for non-contract customers must be requested through
the TAC. Please do not contact either "email@example.com" or
"firstname.lastname@example.org" for software upgrades; faster results will be
obtained by contacting the TAC directly.
There are no system configuration workarounds. Please upgrade to revision
2.5.2 (F) code.
Exploitation and Public Announcements
The Cisco PSIRT is not aware of any public announcements or malicious use
of the vulnerabilities described in this advisory.
This was reported to Cisco by a customer who accidentally discovered this
Status of This Notice: FINAL
This is a final field notice. Although Cisco cannot guarantee the accuracy
of all statements in this notice, all of the facts have been checked to the
best of our ability. Cisco does not anticipate issuing updated versions of
this notice unless there is some material change in the facts. Should there
be a significant change in the facts, Cisco may update this notice.
This notice will be posted on Cisco's Worldwide Web site at
In addition to Worldwide Web posting, a text version of this notice will be
clear-signed with the Cisco PSIRT PGP key and will be posted to the
following e-mail and Usenet news recipients:
* email@example.com (including CERT/CC)
* Various internal Cisco mailing lists
Future updates of this notice, if any, will be placed on Cisco's Worldwide
Web server, but may or may not be actively announced on mailing lists or
newsgroups. Users concerned about this problem are encouraged to check the
URL given above for any updates.
Revision Number 1.0 2001-04-12 Initial public release
Cisco Security Procedures
Complete information on reporting security vulnerabilities in Cisco
products, obtaining assistance with security incidents, and registering to
receive security information from Cisco, is available on Cisco's Worldwide
Web site at
includes instructions for press inquiries regarding Cisco security notices.
This notice is Copyright 2001 by Cisco Systems, Inc. This notice may be
redistributed freely after the release date given at the top of the text,
provided that redistributed copies are complete and unmodified, and include
all date and version information.
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