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AUSCERT External Security Bulletin Redistribution
ESB-2020.2974.3
Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerability
2 September 2020
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AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco IOS XR Software
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Mitigation
CVE Names: CVE-2020-3569 CVE-2020-3566
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxr-dvmrp-memexh-dSmpdvfz
Revision History: September 2 2020: Clarification of potential of IGMP process
crashing and updated mitigations section
September 1 2020: Cisco has added an additional CVE to advisory
and removed a mitigation
August 31 2020: Initial Release
- --------------------------BEGIN INCLUDED TEXT--------------------
Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerabilities
Priority: High
Advisory ID: cisco-sa-iosxr-dvmrp-memexh-dSmpdvfz
First Published: 2020 August 29 03:00 GMT
Last Updated: 2020 September 1 20:02 GMT
Version 2.1: Interim
Workarounds: No workarounds available
Cisco Bug IDs: CSCvr86414CSCvv54838
CVE-2020-3566
CVE-2020-3569
CWE-400
Summary
o Multiple vulnerabilities in the Distance Vector Multicast Routing Protocol
(DVMRP) feature of Cisco IOS XR Software could allow an unauthenticated,
remote attacker to either immediately crash the Internet Group Management
Protocol (IGMP) process or make it consume available memory and eventually
crash. The memory consumption may negatively impact other processes that
are running on the device.
These vulnerabilities are due to the incorrect handling of IGMP packets. An
attacker could exploit these vulnerabilities by sending crafted IGMP
traffic to an affected device. A successful exploit could allow the
attacker to immediately crash the IGMP process or cause memory exhaustion,
resulting in other processes becoming unstable. These processes may
include, but are not limited to, interior and exterior routing protocols.
Cisco will release software updates that address these vulnerabilities.
There are no workarounds that address these vulnerabilities. There are
multiple mitigations available to customers depending on their needs.
This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-iosxr-dvmrp-memexh-dSmpdvfz
Affected Products
o Vulnerable Products
These vulnerabilities affect any Cisco device that is running any release
of Cisco IOS XR Software if an active interface is configured under
multicast routing and it is receiving DVMRP traffic.
Determine Whether Multicast Routing Is Enabled
An administrator can determine whether multicast routing is enabled on a
device by issuing the show igmp interface command. The following output
shows a device with multicast routing enabled:
RP/0/0/CPU0:router# show igmp interface
Loopback0 is up, line protocol is up
Internet address is 10.144.144.144/32
IGMP is enabled on interface
Current IGMP version is 3
IGMP query interval is 60 seconds
IGMP querier timeout is 125 seconds
IGMP max query response time is 10 seconds
Last member query response interval is 1 seconds
IGMP activity: 3 joins, 0 leaves
IGMP querying router is 10.144.144.144 (this system)
TenGigE0/4/0/0 is up, line protocol is up
Internet address is 10.114.8.44/24
IGMP is enabled on interface
Current IGMP version is 3
IGMP query interval is 60 seconds
IGMP querier timeout is 125 seconds
IGMP max query response time is 10 seconds
Last member query response interval is 1 seconds
IGMP activity: 9 joins, 4 leaves
IGMP querying router is 10.114.8.11
If the output of show igmp interface is empty, multicast routing is not
enabled and the device is not affected by these vulnerabilities.
Determine Whether the Device Is Receiving DVMRP Traffic
An administrator can determine whether the device is receiving DVMRP
traffic by issuing the show igmp traffic command. The following output
shows a device that is receiving DVMRP traffic:
RP/0/0/CPU0:router#show igmp traffic
Fri Feb 13 12:00:00.000 UTC
IGMP Traffic Counters
Elapsed time since counters cleared: 01:09:27
Received Sent
Valid IGMP Packets 380220 301
Queries 0 143
Reports 0 158
Leaves 0 0
Mtrace packets 0 0
DVMRP packets 380220 0
If the DVMRP packets entry contains values of zero in the first column, and
the counters remain zero on subsequent execution of the command, the device
is not receiving DVMRP traffic.
Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory
are known to be affected by these vulnerabilities.
Details
o These vulnerabilities result in memory exhaustion, which can impact other
processes on the device. It is possible to recover the memory consumed by
the IGMP process by restarting the IGMP process with the process restart
igmp command as follows:
RP/0/0/CPU0:router# process restart igmp
In the case of an immediate IGMP process crash, it is not necessary to
manually restart the IGMP process because the system has already performed
that action. This automated restart will recover the consumed memory.
When considering mitigations, it should be understood that for the memory
exhaustion case, the rate limiter and the access control methods are
effective. For the immediate IGMP process crash case, only the access
control method is effective.
Indicators of Compromise
o When a device is experiencing memory exhaustion based on exploitation of
these vulnerabilities, the following messages may be seen in the system
logs:
RP/0/RSP1/CPU0:Aug 28 03:46:10.375 UTC: raw_ip[399]: %PKT_INFRA-PQMON-6-QUEUE_DROP : Taildrop on XIPC queue 1 owned by igmp (jid=1175)
RP/0/RSP0/CPU0:Aug 28 03:46:10.380 UTC: raw_ip[399]: %PKT_INFRA-PQMON-6-QUEUE_DROP : Taildrop on XIPC queue 1 owned by igmp (jid=1175)
RP/0/RSP0/CPU0:Aug 28 03:49:22.850 UTC: dumper[61]: %OS-DUMPER-7-DUMP_REQUEST : Dump request for process pkg/bin/igmp
RP/0/RSP0/CPU0:Aug 28 03:49:22.851 UTC: dumper[61]: %OS-DUMPER-7-DUMP_ATTRIBUTE : Dump request with attribute 7 for process pkg/bin/igmp
RP/0/RSP0/CPU0:Aug 28 03:49:22.851 UTC: dumper[61]: %OS-DUMPER-4-SIGSEGV : Thread 9 received SIGSEGV - Segmentation Fault
When a device has experienced a crash of the IGMP process, the following
messages may be seen in the system logs:
RP/0/RSP0/CPU0:Aug 30 17:21:47.653 UTC: igmp[1169]: %HA-HA_WD_LIB-4-RLIMIT : wd_handle_sigxfsz: Reached 90% of RLIMIT_DATA
RP/0/RSP0/CPU0:Aug 30 17:21:47.653 UTC: igmp[1169]: %ROUTING-IPV4_IGMP-4-OOM_STATE_THROTTLE : Received Critical memory depletion warning, stop creating new igmp state
RP/0/RSP1/CPU0:Aug 30 17:23:50.442 UTC: sysmgr[94]: igmp(1) (jid 1169) (pid 121667828) (fail_count 2) abnormally terminated, restart scheduled
Workarounds
o Although there are no workarounds for these vulnerabilities, there are
multiple mitigations available to customers depending on their needs.
As a mitigation for the memory exhaustion case, it is recommended that
customers implement a rate limiter. This will require that customers
understand their current rate of IGMP traffic and set a rate lower than the
current average rate. It is worth noting that there is a default limiter in
place. In configuration mode, the customer can enter the lpts pifib
hardware police flow igmp rate command as follows:
RP/0/0/CPU0:router(config)# lpts pifib hardware police flow igmp rate
This command will not remove the exploit vector. However, the command will
reduce the traffic rate and increase the time necessary for successful
exploitation. The customer can use this time to perform recovery actions.
As a mitigation for both the memory exhaustion case and the immediate IGMP
process crash case, customers may implement an access control entry (ACE)
to an existing interface access control list (ACL). Alternatively, the
customer can create a new ACL for a specific interface that denies DVMRP
traffic inbound on that interface. The following example creates an ACL and
denies DVMRP traffic:
RP/0/0/CPU0:router(config)# ipv4 access-list deny igmp any any dvmrp
Fixed Software
o Cisco will release free software updates that address the vulnerabilities
described in this advisory. Customers may only install and expect support
for software versions and feature sets for which they have purchased a
license. By installing, downloading, accessing, or otherwise using such
software upgrades, customers agree to follow the terms of the Cisco
software license:
https://www.cisco.com/c/en/us/products/end-user-license-agreement.html
Additionally, customers may only download software for which they have a
valid license, procured from Cisco directly, or through a Cisco authorized
reseller or partner. In most cases this will be a maintenance upgrade to
software that was previously purchased. Free security software updates do
not entitle customers to a new software license, additional software
feature sets, or major revision upgrades.
When considering software upgrades , customers are advised to regularly
consult the advisories for Cisco products, which are available from the
Cisco Security Advisories page , to determine exposure and a complete
upgrade solution.
In all cases, customers should ensure that the devices to be upgraded
contain sufficient memory and confirm that current hardware and software
configurations will continue to be supported properly by the new release.
If the information is not clear, customers are advised to contact the Cisco
Technical Assistance Center (TAC) or their contracted maintenance
providers.
Customers Without Service Contracts
Customers who purchase directly from Cisco but do not hold a Cisco service
contract and customers who make purchases through third-party vendors but
are unsuccessful in obtaining fixed software through their point of sale
should obtain upgrades by contacting the Cisco TAC: https://www.cisco.com/c
/en/us/support/web/tsd-cisco-worldwide-contacts.html
Customers should have the product serial number available and be prepared
to provide the URL of this advisory as evidence of entitlement to a free
upgrade.
Fixed Releases
Cisco will release software updates that address these vulnerabilities. As
fixed releases and SMUs become available, this advisory will be updated.
Exploitation and Public Announcements
o On August 28, 2020, the Cisco Product Security Incident Response Team
(PSIRT) became aware of attempted exploitation of these vulnerabilities in
the wild. For affected products, Cisco recommends implementing a mitigation
that is appropriate for the customer's environment.
Source
o These vulnerabilities were found during the resolution of a Cisco TAC
support case.
Cisco Security Vulnerability Policy
o To learn about Cisco security vulnerability disclosure policies and
publications, see the Security Vulnerability Policy . This document also
contains instructions for obtaining fixed software and receiving security
vulnerability information from Cisco.
Action Links for This Advisory
o Snort Rule 54902
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-iosxr-dvmrp-memexh-dSmpdvfz
Revision History
o +---------+------------------------+--------------+---------+-------------+
| Version | Description | Section | Status | Date |
+---------+------------------------+--------------+---------+-------------+
| | Clarified the | Summary, | | |
| | potential of the IGMP | Vulnerable | | |
| | process crashing. | Products, | | |
| | Added DVMRP traffic | Details, | | |
| 2.1 | requirement. Updated | Indicators | Interim | 2020-SEP-01 |
| | the mitigations | of | | |
| | according to specific | Compromise, | | |
| | exploit outcome. | and | | |
| | | Workarounds | | |
+---------+------------------------+--------------+---------+-------------+
| | Added another Cisco | | | |
| | bug ID and CVE ID. | | | |
| | Updated wording | | | |
| | throughout to reflect | | | |
| | multiple | Header, | | |
| | vulnerabilities. | Vulnerable | | |
| 2.0 | Corrected a typo in | Products, | Interim | 2020-AUG-31 |
| | the Determine Whether | and | | |
| | the Device Is | Workarounds | | |
| | Receiving DVMRP | | | |
| | Traffic instructions. | | | |
| | Removed an ineffective | | | |
| | mitigation. | | | |
+---------+------------------------+--------------+---------+-------------+
| 1.0 | Initial public | - | Interim | 2020-AUG-29 |
| | release. | | | |
+---------+------------------------+--------------+---------+-------------+
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