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AUSCERT External Security Bulletin Redistribution
ESB-2023.1722
Cisco IOS XE Software Fragmented Tunnel Protocol Packet
Denial of Service Vulnerability
23 March 2023
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco IOS XE Software
Publisher: Cisco Systems
Operating System: Cisco
Resolution: Patch/Upgrade
CVE Names: CVE-2023-20072
Original Bulletin:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-gre-crash-p6nE5Sq5
Comment: CVSS (Max): 8.6 CVE-2023-20072 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H)
CVSS Source: Cisco Systems
Calculator: https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
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Cisco IOS XE Software Fragmented Tunnel Protocol Packet Denial of Service
Vulnerability
Priority: High
Advisory ID: cisco-sa-ios-gre-crash-p6nE5Sq5
First Published: 2023 March 22 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCwc32921
CVE Names: CVE-2023-20072
Summary
o A vulnerability in the fragmentation handling code of tunnel protocol
packets in Cisco IOS XE Software could allow an unauthenticated, remote
attacker to cause an affected system to reload, resulting in a denial of
service (DoS) condition.
This vulnerability is due to the improper handling of large fragmented
tunnel protocol packets. One example of a tunnel protocol is Generic
Routing Encapsulation (GRE). An attacker could exploit this vulnerability
by sending crafted fragmented packets to an affected system. A successful
exploit could allow the attacker to cause the affected system to reload,
resulting in a DoS condition.
Note: Only traffic directed to the affected system can be used to exploit
this vulnerability.
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://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-gre-crash-p6nE5Sq5
This advisory is part of the March 2023 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 2023
Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled
Publication .
Affected Products
o Vulnerable Products
This vulnerability affects Cisco products if they are running Cisco IOS XE
Software releases 17.9.1, 17.9.1a, or 17.9.1w and have a tunnel interface
configured.
For more information about which Cisco software releases are vulnerable,
see the Fixed Software section of this advisory.
Determine the Device Configuration
To determine whether a device is running Cisco IOS XE Software with a
tunnel interface configured, run show ip interface brief | count Tun as
shown in the following example:
Route# show ip interface brief | count Tun
Number of lines which match regexp = 1
If the regexp = 0, there are no tunnel interfaces configured, and the
device is not affected by this vulnerability.
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
Meraki products
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 with service contracts that entitle
them to regular software updates should obtain security fixes through their
usual update channels.
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.
The Cisco Support and Downloads page on Cisco.com provides information
about licensing and downloads. This page can also display customer device
support coverage for customers who use the My Devices tool.
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 . This tool
identifies any Cisco security advisories that impact a specific software
release and the earliest release that fixes the vulnerabilities that are
described in each advisory ("First Fixed"). If applicable, the tool also
returns the earliest release that fixes all the vulnerabilities that are
described in all the advisories that the Software Checker identifies
("Combined First Fixed").
To use the tool, go to the Cisco Software Checker page and follow the
instructions. Alternatively, use the following form to determine whether a
release is affected by any Cisco Security Advisory. To use the form, follow
these steps:
1. Choose which advisories the tool will search-only this advisory, only
advisories with a Critical or High Security Impact Rating (SIR) , or
all advisories.
2. Enter a release number-for example, 15.9(3)M2 or 17.3.3.
3. Click Check .
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 internal security testing.
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.
Subscribe to Cisco Security Notifications
o Subscribe
Related to This Advisory
o Cisco Event Response: March 2023 Semiannual Cisco IOS and IOS XE Software
Security Advisory Bundled Publication
URL
o https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-gre-crash-p6nE5Sq5
Revision History
o +----------+---------------------------+----------+--------+--------------+
| Version | Description | Section | Status | Date |
+----------+---------------------------+----------+--------+--------------+
| 1.0 | Initial public release. | - | Final | 2023-MAR-22 |
+----------+---------------------------+----------+--------+--------------+
Legal Disclaimer
o THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND
OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR
FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT
OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES
THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.
A standalone copy or paraphrase of the text of this document that omits the
distribution URL is an uncontrolled copy and may lack important information
or contain factual errors. The information in this document is intended for
end users of Cisco products.
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