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AUSCERT External Security Bulletin Redistribution
ESB-2021.1049
Cisco IOS XE Software DECnet Phase IV/OSI Denial of Service Vulnerability
25 March 2021
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco IOS XE Software DECnet Phase IV/OSI
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2021-1352
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxe-decnet-dos-cuPWDkyL
- --------------------------BEGIN INCLUDED TEXT--------------------
Cisco IOS XE Software DECnet Phase IV/OSI Denial of Service Vulnerability
Priority: High
Advisory ID: cisco-sa-iosxe-decnet-dos-cuPWDkyL
First Published: 2021 March 24 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvv51476
CVE Names: CVE-2021-1352
CWEs: CWE-823
Summary
o A vulnerability in the DECnet Phase IV and DECnet/OSI protocol processing
of Cisco IOS XE Software could allow an unauthenticated, adjacent attacker
to cause a denial of service (DoS) condition on an affected device.
The vulnerability is due to insufficient input validation of DECnet traffic
that is received by an affected device. An attacker could exploit this
vulnerability by sending DECnet traffic to an affected device. A successful
exploit could allow the attacker to cause the affected device to reload,
resulting in a DoS condition.
Cisco has released software updates that address this vulnerability. There
are no workarounds that address this vulnerability.
This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxe-decnet-dos-cuPWDkyL
This advisory is part of the March 2021 release of the Cisco IOS and IOS XE
Software Security Advisory Bundled Publication. For a complete list of the
advisories and links to them, see Cisco Event Response: March 2021
Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled
Publication .
Affected Products
o Vulnerable Products
This vulnerability affects Cisco devices if they are running a vulnerable
release of Cisco IOS XE Software and have either the DECnet Phase IV or
DECnet/OSI protocol enabled. DECnet is not enabled by default.
For information about which Cisco software releases are vulnerable, see the
Fixed Software section of this advisory.
Determine the Device Configuration
To determine if DECnet is enabled, use the show decnet interface command.
The following example shows output for a device that is configured for
DECnet on the GigabitEthernet0/0/0 interface:
router# show decnet interface
.
.
.
GigabitEthernet0/0/0 is up, line protocol is up, encapsulation is ARPA
Interface cost is 1, priority is 64, DECnet network: 0
We are the designated router
Sending HELLOs every 15 seconds, routing updates 40 seconds
.
.
.
A device is not affected by this vulnerability if DECnet is not enabled, as
indicated by the following example of output for the show decnet interface
command:
router#show decnet interface
% DECnet is not enabled
Furthermore, a device is not affected by this vulnerability if DECnet
protocol processing is not enabled for all interfaces, as indicated by the
following example of output for the show decnet interface command:
router#show decnet interface
.
.
.
GigabitEthernet0/0/0 is up, line protocol is up, encapsulation is ARPA
DECnet protocol processing not enabled
.
.
.
Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory
are known to be affected by this vulnerability.
Cisco has confirmed that this vulnerability does not affect the following
Cisco products:
IOS Software
IOS XR Software
NX-OS Software
Workarounds
o There are no workarounds that address this vulnerability.
Fixed Software
o Cisco has released free software updates that address the vulnerability
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.
Cisco IOS and IOS XE Software
To help customers determine their exposure to vulnerabilities in Cisco IOS
and IOS XE Software, Cisco provides the Cisco Software Checker to identify
any Cisco Security Advisories that impact a specific software release and
the earliest release that fixes the vulnerabilities described in each
advisory ("First Fixed"). If applicable, the tool also returns the earliest
release that fixes all the vulnerabilities described in all the advisories
identified ("Combined First Fixed").
Customers can use the Cisco Software Checker to search advisories in the
following ways:
Choose the software and one or more releases
Upload a .txt file that includes a list of specific releases
Enter the output of the show version command
After initiating a search, customers can customize the search to include
all Cisco Security Advisories, a specific advisory, or all advisories in
the most recent bundled publication.
Customers can also use the following form to determine whether a release is
affected by any Cisco Security Advisory by entering a Cisco IOS or IOS XE
Software release-for example, 15.1(4)M2 or 3.13.8S.
By default, the Cisco Software Checker includes results only for
vulnerabilities that have a Critical or High Security Impact Rating (SIR).
To include results for Medium SIR vulnerabilities, customers can use the
Cisco Software Checker on Cisco.com and check the Medium check box in the
drop-down list under Impact Rating when customizing a search.
For a mapping of Cisco IOS XE Software releases to Cisco IOS Software
releases, refer to the Cisco IOS XE 2 Release Notes , Cisco IOS XE 3S
Release Notes , or Cisco IOS XE 3SG Release Notes , depending on the Cisco
IOS XE Software release.
Exploitation and Public Announcements
o The Cisco Product Security Incident Response Team (PSIRT) is not aware of
any public announcements or malicious use of the vulnerability that is
described in this advisory.
Source
o This vulnerability was 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.
Related to This Advisory
o Cisco Event Response: March 2021 Semiannual Cisco IOS and IOS XE Software
Security Advisory Bundled Publication
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxe-decnet-dos-cuPWDkyL
Revision History
o +----------+---------------------------+----------+--------+--------------+
| Version | Description | Section | Status | Date |
+----------+---------------------------+----------+--------+--------------+
| 1.0 | Initial public release. | - | Final | 2021-MAR-24 |
+----------+---------------------------+----------+--------+--------------+
- --------------------------END INCLUDED TEXT--------------------
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