ESB-2021.3600

Operating System:

[Cisco]

Published:

28 October 2021

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Resources > Security Bulletins > ESB-2021.3600

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AUSCERT External Security Bulletin Redistribution

ESB-2021.3600
Multiple Cisco Products Snort Vulnerabilities
28 October 2021

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AusCERT Security Bulletin Summary
---------------------------------

Product: Firepower Threat Defense (FTD)
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2021-40116 CVE-2021-40114

Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort-dos-s2R7W9UU
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort-dos-RywH7ezM

Comment: This bulletin contains two (2) Cisco Systems security advisories.

- --------------------------BEGIN INCLUDED TEXT--------------------

Multiple Cisco Products Snort Memory Leak Denial of Service Vulnerability

Priority: Medium
Advisory ID: cisco-sa-snort-dos-s2R7W9UU
First Published: 2021 October 27 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvt57503 CSCvx29001
CVE Names: CVE-2021-40114
CWEs: CWE-770

Summary

o Multiple Cisco products are affected by a vulnerability in the way the
Snort detection engine processes ICMP traffic that could allow an
unauthenticated, remote attacker to cause a denial of service (DoS)
condition on an affected device.

The vulnerability is due to improper memory resource management while the
Snort detection engine is processing ICMP packets. An attacker could
exploit this vulnerability by sending a series of ICMP packets through an
affected device. A successful exploit could allow the attacker to exhaust
resources on the affected device, causing the device to reload.

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-snort-dos-s2R7W9UU

This advisory is part of the October 2021 release of the Cisco ASA, FTD,
and FMC Security Advisory Bundled publication. For a complete list of the
advisories and links to them, see Cisco Event Response: October 2021 Cisco
ASA, FMC, and FTD Software Security Advisory Bundled Publication .

Affected Products

o Vulnerable Products

At the time of publication, this vulnerability affected all open source
Snort project releases earlier than Release 2.9.18. For more information on
open source Snort, see the Snort website .

Impact to Cisco Products

At the time of publication, this vulnerability affected the following Cisco
products if they were running a vulnerable release of Cisco Software:

Firepower Threat Defense (FTD) Software - All platforms

At the time of publication, this vulnerability affected the following Cisco
products if they were running a release earlier than the first fixed
release of Cisco Unified Threat Defense (UTD) Snort Intrusion Prevention
System (IPS) Engine for Cisco IOS XE Software or Cisco UTD Engine for Cisco
IOS XE SD-WAN Software.

Note : UTD is not installed on these devices by default:

1000 Series Integrated Services Routers (ISRs)
4000 Series Integrated Services Routers (ISRs)
Catalyst 8000V Edge Software
Catalyst 8200 Series Edge Platforms
Catalyst 8300 Series Edge Platforms
Cloud Services Routers 1000V Series
Integrated Services Virtual Routers (ISRv)

For information about which Cisco software releases were vulnerable at the
time of publication, see the Fixed Software section of this advisory. See
the Details section in the bug ID(s) at the top of this advisory for the
most complete and current information.

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:

Adaptive Security Appliance (ASA) Software
Catalyst 8500 Series Edge Platforms
Catalyst 8500L Series Edge Platforms
Firepower Management Center (FMC) Software
Meraki Security Appliances

Workarounds

o There are no workarounds that address this vulnerability.

Fixed Software

o 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.

Fixed Releases

At the time of publication, the release information in the following table
(s) was accurate. See the Details section in the bug ID(s) at the top of
this advisory for the most complete and current information.

The left column lists Cisco software releases, and the right column
indicates whether a release was affected by the vulnerability described in
this advisory and which release included the fix for this vulnerability.

Cisco FTD Software

FTD Software Release First Fixed Release for This Vulnerability
6.2.2 and earlier ^1 Migrate to a fixed release.
6.2.3 Migrate to a fixed release.
6.3.0 ^1 Migrate to a fixed release.
6.4.0 6.4.0.12
6.5.0 ^1 Migrate to a fixed release.
6.6.0 6.6.3
6.7.0 6.7.0.2
7.0.0 Not vulnerable.

1. Cisco FMC and FTD Software releases 6.2.2 and earlier, as well as
releases 6.3.0 and 6.5.0, have reached end of software maintenance .
Customers are advised to migrate to a supported release that includes the
fix for this vulnerability.

For instructions on upgrading your FTD device, see Cisco Firepower
Management Center Upgrade Guide .

Cisco UTD Software

UTD Software Release First Fixed Release for This Vulnerability
16.12 16.12.6
17.3 17.3.4a
17.4 17.4.2
17.5 Not vulnerable.
17.6 Not vulnerable.
17.7 Not vulnerable.

Snort Software Release

Snort Major Release First Fixed Release for This Vulnerability
2.x 2.9.18
3.x Not vulnerable.

The Cisco Product Security Incident Response Team (PSIRT) validates only
the affected and fixed release information that is documented in this
advisory.

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.

Related to This Advisory

o Cisco Event Response: October 2021 Cisco ASA, FMC, and FTD Software
Security Advisory Bundled Publication

URL

o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort-dos-s2R7W9UU

Revision History

o +----------+---------------------------+----------+--------+--------------+
| Version | Description | Section | Status | Date |
+----------+---------------------------+----------+--------+--------------+
| 1.0 | Initial public release. | - | Final | 2021-OCT-27 |
+----------+---------------------------+----------+--------+--------------+

- ------------------------------------------------------------------------------------------------------

Multiple Cisco Products Snort Rule Denial of Service Vulnerability

Priority: High
Advisory ID: cisco-sa-snort-dos-RywH7ezM
First Published: 2021 October 27 16:00 GMT
Version 1.0: Final
Workarounds: Yes
Cisco Bug IDs: CSCvy66065
CVE Names: CVE-2021-40116
CWEs: CWE-241

Summary

o Multiple Cisco products are affected by a vulnerability in Snort rules that
could allow an unauthenticated, remote attacker to cause a denial of
service (DoS) condition on an affected device.

The vulnerability is due to improper handling of the Block with Reset or
Interactive Block with Reset actions if a rule is configured without proper
constraints. An attacker could exploit this vulnerability by sending a
crafted IP packet to the affected device. A successful exploit could allow
the attacker to cause through traffic to be dropped.

Note: Only products with Snort3 configured and either a rule with Block
with Reset or Interactive Block with Reset actions configured are
vulnerable. Products configured with Snort2 are not vulnerable.

Cisco has released software updates that address this vulnerability. There
are workarounds that address this vulnerability.

This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort-dos-RywH7ezM

Affected Products

o Vulnerable Products

This vulnerability affects all open source Snort3 project releases earlier
than Release 3.1.0.100. For more information on open source Snort, see the
Snort website .

Impact to Cisco Products

This vulnerability affects all platforms if they are running a vulnerable
release of Cisco Firepower Threat Defense (FTD) Software and are configured
in a vulnerable manner as indicated in the following sections.

Firepower Threat Defense (FTD) devices managed by Firepower Device
Management (FDM) Software are not vulnerable because they do not have Block
with Reset or Interactive Block with Reset actions.

Three conditions for Firewall Management Center (FMC) managed devices must
be met for the device to be vulnerable:

The device must be running Snort3.
The device must have a rule configured with a Block with Reset or
Interactive Block with Reset action.
The rule configured with the Reset action does not specify an
application or protocol (TCP or UDP) within the rule.

For information about which Cisco software releases are vulnerable, see the
Fixed Software section of this advisory.

Determine FTD Configuration

To determine if Snort3 is configured

1. Go to the FMC web interface.
2. Go to the Devices page and then the Device Management tab.
3. Select the FTD device to check. Choose Edit .
4. Go to the Device tab and look in the Inspection Engine area.
5. This will list either Snort2 or Snort 3.
If Snort2 is listed, the device is not vulnerable.
If Snort3 is listed, the device could be vulnerable.

To determine if a rule with a Block with Reset or Interactive Block with
Reset action is configured

1. Go to the FMC web interface.
2. Go to the Policies page and then the Access Control tab.
3. Select the Policy to review and choose Edit .
4. Look under the Action column for each rule in that policy.
If Block with Reset or Interactive Block with Reset is not listed
under actions, the device is not vulnerable.
If Block with Reset or Interactive Block with Reset is listed under
actions, the device could be vulnerable.

To determine if the rule with a Reset action has a vulnerable configuration

If a device is running Snort3 and has a rule with Block with Reset or
Interactive Block with Reset action configured, the following tables can be
used to determine if the rule is configured in a vulnerable or
non-vulnerable configuration.

The tables show configuration information for an FTD device as viewed on an
FMC.

Vulnerable Configuration

If the rule is configured without calling out either the application or the
protocol (TCP or UDP), the device is configured in a vulnerable manner.

Here are examples of a rule with a vulnerable configuration

Non-Vulnerable Configuration

If the rule is configured by calling out either the application or the
protocol (TCP or UDP), the device is configured in non-vulnerable manner.

Application Template and Example

The following are templates of non-vulnerable configurations calling out an
application. The example shows the minimum configuration required.

Rule Source Destination Source Destination VLAN Users Applications Source Destination URLs Source Destination Actions
Name Zone Zone Network Network Tags Ports Ports SGT SGT
{application Block with
Ex1 any any any any any any specified any any any any any Reset
here}
{application Interactive
Ex2 any any any any any any specified any any any any any Block with
here} Reset

The following are examples of non-vulnerable configurations calling out an
application. The example shows the minimum configuration required.

Rule Source Destination Source Destination VLAN Users Applications Source Destination URLs Source Destination Actions
Name Zone Zone Network Network Tags Ports Ports SGT SGT
Ex1 any any any any any any Cisco Jabber any any any any any Block with
Reset
Interactive
Ex2 any any any any any any Cisco Jabber any any any any any Block with
Reset

Protocol Template and Example

The following are templates of non-vulnerable configurations calling out
the protocol (TCP or UDP). The example shows the minimum configuration
required.

Rule Source Destination Source Destination VLAN Users Applications Source Destination URLs Source Destination Actions
Name Zone Zone Network Network Tags Ports Ports SGT SGT
{tcp or {tcp or upd
Ex1 any any any any any any any upd specified any any any Block with
specified here} Reset
here}
{tcp or {tcp or upd Interactive
Ex2 any any any any any any any upd specified any any any Block with
specified here} Reset
here}

The following are examples of non-vulnerable configurations calling out the
protocol (TCP or UDP). The example shows the minimum configuration
required.

Rule Source Destination Source Destination VLAN Users Applications Source Destination URLs Source Destination Actions
Name Zone Zone Network Network Tags Ports Ports SGT SGT
Ex1 any any any any any any any tcp tcp any any any Block with
Reset
Interactive
Ex2 any any any any any any any tcp tcp any any any Block with
Reset
Ex3 any any any any any any any udp udp any any any Block with
Reset
Interactive
Ex4 any any any any any any any udp udp any any any Block with
Reset

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 any open source
Snort2 project releases.

Cisco has confirmed that this vulnerability does not affect the following
Cisco products:

Adaptive Security Appliance (ASA) Software
1000 Series Integrated Services Routers (ISRs)
4000 Series Integrated Services Routers (ISRs)
Catalyst 8000V Edge Software
Catalyst 8200 Series Edge Platforms
Catalyst 8300 Series Edge Platforms
Catalyst 8500 Series Edge Platforms
Catalyst 8500L Series Edge Platforms
Cloud Services Router 1000V Series
Firepower Management Center (FMC) Software
Integrated Services Virtual Router (ISRv)
Meraki Security Appliances

Workarounds

o There are workarounds that addresses this vulnerability.

While these workarounds have been deployed and were proven successful in a
test environment, customers should determine the applicability and
effectiveness in their own environment and under their own use conditions.
Customers should be aware that any workaround or mitigation that is
implemented may negatively impact the functionality or performance of their
network based on intrinsic customer deployment scenarios and limitations.
Customers should not deploy any workarounds or mitigations before first
evaluating the applicability to their own environment and any impact to
such environment.

Note: There are three workarounds for this issue. Implementing any of the
workarounds is sufficient. Two or more workarounds do not need to be
implemented.

Workaround 1

The first workaround is to change the Snort inspection engine from Snort3
to Snort2. See the configuration guide or support team for potential
impacts. The steps to revert to Snort2 are as follows:

1. Go to the FMC web interface
2. Go to the Devices page and then the Device Management tab.
3. Select the FTD device to check. Choose Edit .
4. Go to the Device tab and look in the Inspection Engine area.
5. Choose the Revert to Snort2 option.

Workaround 2

The second workaround is to change all rule actions from Block with Reset
or Interactive Block with Reset to another action. See the configuration
guide or support team for potential impacts. The steps are as follows:

1. Go to the FMC web interface
2. Go to the Policies page and then the Access Control tab.
3. Select the Policy to review and choose Edit .
4. Find a rule that has a Reset action and choose Edit .
5. Change the action from Block with Reset or Interactive Block with Reset
to another action.

Workaround 3

The third workaround involves narrowing the firewall reset rule to block
TCP and/or UDP directly or by specifying an application that runs over UDP
or TCP. See the Vulnerable Products section for examples of vulnerable and
non-vulnerable configurations.

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.

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

Customers are advised to upgrade to an appropriate fixed software release
as indicated in the following table(s):

Cisco FTD Software

In the following table(s), the left column lists Cisco software releases.
The center column indicates whether a release is affected by the
vulnerability described in this advisory and the first release that
includes the fix for this vulnerability. The right column indicates whether
a release is affected by any of the Critical or High SIR vulnerabilities
described in this bundle and which release includes fixes for those
vulnerabilities.

FTD First Fixed Release First Fixed Release for All
Software for This Vulnerability Vulnerabilities Described in the Bundle
Release of Advisories
6.2.2 and Not vulnerable. Migrate to a fixed release.
earlier ^1
6.2.3 Not vulnerable. Migrate to a fixed release.
6.3.0 ^1 Not vulnerable. Migrate to a fixed release.
6.4.0 Not vulnerable. 6.4.0.13 (Nov 2021)
6.5.0 ^1 Not vulnerable. Migrate to a fixed release.
6.6.0 Not vulnerable. 6.6.5.1 (Nov 2021)
6.7.0 ^2 Not vulnerable. 6.7.0.3 (Jan 2022)
7.0.0 7.0.1 7.0.1

2. The Snort3 Inspection Engine option was first available in FTD devices
managed by FDM in 6.7.0. This option was not available for FMC managed
devices until 7.0.0. Only FTD devices managed by FTD are vulnerable to this
issue.

For instructions on upgrading your FTD device, see Cisco Firepower
Management Center Upgrade Guide .

Open Source Snort

For more information on open source Snort, see the Snort website .

Snort Release First Fixed Release for This Vulnerability
2.x Not vulnerable.
3.x 3.1.0.100

The Cisco Product Security Incident Response Team (PSIRT) validates only
the affected and fixed release information that is documented in this
advisory.

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

Related to This Advisory

o Cisco Event Response: October 2021 Cisco ASA, FMC, and FTD Software
Security Advisory Bundled Publication

URL

o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort-dos-RywH7ezM

Revision History

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