Full Disclosure mailing list archives

Re: on topic - cisco snmp


From: Ilker Temir <itemir () cisco com>
Date: Sat, 7 Jun 2003 17:44:43 +0200 (CEST)

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This is in response to the e-mail sent by Lee E. Rian. The original e-mail
is available at
http://lists.netsys.com/pipermail/full-disclosure/2003-June/010153.html

Hello Lee,

Thank you for notifying us about this issue. We have updated the examples at
http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a00800948e6.shtml
and excluded the MIBs that may create a security exposure.

We are always very interested in vulnerability reports regarding our
products and welcome the chance to work with security researchers. Such
reports should be directly sent to our team at psirt () cisco com or to
security-alert () cisco com for emergency response.

Thank you again,

Regards,
- --
Ilker Temir
Incident Manager, PSIRT
Cisco Systems, Inc.
+32 2 704-6031
http://www.cisco.com/go/psirt

On Fri, 6 Jun 2003 lee.e.rian () census gov wrote:

If you follow Cisco's suggested work-around for SNMP causes high CPU
utilization you might be exposing the write community string.

http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a00800948e6.shtml
has the following instructions:

   To avoid performance issues, force the router to prematurely end queries
   for the route table from the network management system server. Configure
   the router to respond with a complete message as soon as it receives the
   start of a request for the route table, as follows:
   snmp-server view cutdown internet included
   snmp-server view cutdown ipRouteTable excluded
   snmp-server view cutdown ipNetToMediaTable excluded
   snmp-server view cutdown at excluded
   snmp-server community public view cutdown RO
   snmp-server community private view cutdown RW

The problem is that the View-based Access Control MIB is now included in
the read-only view:
snmpwalk -c public -v 2c c800 vacmAccessWriteViewName
.iso.org.dod.internet.snmpV2.snmpModules.snmpVacmMIB.vacmMIBObjects.vacmAccessTable.vacmAccessEntry.vacmAccessWriteViewName."public"."".1.noAuthNoPriv
 =
.iso.org.dod.internet.snmpV2.snmpModules.snmpVacmMIB.vacmMIBObjects.vacmAccessTable.vacmAccessEntry.vacmAccessWriteViewName."public"."".2.noAuthNoPriv
 =
.iso.org.dod.internet.snmpV2.snmpModules.snmpVacmMIB.vacmMIBObjects.vacmAccessTable.vacmAccessEntry.vacmAccessWriteViewName."private"."".1.noAuthNoPriv
 = cutdown
.iso.org.dod.internet.snmpV2.snmpModules.snmpVacmMIB.vacmMIBObjects.vacmAccessTable.vacmAccessEntry.vacmAccessWriteViewName."private"."".2.noAuthNoPriv
 = cutdown

Fix is to remove the Vacm MIB from the view by adding
snmp-server view cutdown internet.6.3.16 excluded

c800#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
c800(config)#snmp-server view cutdown internet.6.3.16 excluded
c800(config)#end
c800#

snmpwalk -c public -v 2c c800 vacmAccessWriteViewName
.iso.org.dod.internet.snmpV2.snmpModules.snmpVacmMIB.vacmMIBObjects.vacmAccessTable.vacmAccessEntry.vacmAccessWriteViewName
 = No more variables left in this MIB View


Lee



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