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AUSCERT External Security Bulletin Redistribution
ESB-2021.0140.2
Multiple Cisco Products Snort Application Detection Engine
Policy Bypass Vulnerability
15 November 2021
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AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco Products
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Reduced Security -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2021-1236
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort-app-bypass-cSBYCATq
Revision History: November 15 2021: Updated vulnerability information for Cisco UTD Engine requirements
January 14 2021: Initial Release
- --------------------------BEGIN INCLUDED TEXT--------------------
Multiple Cisco Products Snort Application Detection Engine Policy Bypass
Vulnerability
Priority: Medium
Advisory ID: cisco-sa-snort-app-bypass-cSBYCATq
First Published: 2021 January 13 16:00 GMT
Last Updated: 2021 November 12 21:04 GMT
Version 1.1: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvs85467 CSCvu21318
CVE Names: CVE-2021-1236
CWEs: CWE-670
CVSS Score:
4.0 AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N/E:X/RL:X/RC:X
Summary
o Multiple Cisco products are affected by a vulnerability in the Snort
application detection engine that could allow an unauthenticated, remote
attacker to bypass the configured policies on an affected system.
The vulnerability is due to a flaw in the detection algorithm. An attacker
could exploit this vulnerability by sending crafted packets that would flow
through an affected system. A successful exploit could allow the attacker
to bypass the configured policies and deliver a malicious payload to the
protected network.
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-app-bypass-cSBYCATq
Affected Products
o Vulnerable Products
At the time of publication, this vulnerability affected all open source
Snort project releases earlier than Release 2.9.14. For more information,
see the Snort website .
At the time of publication, this vulnerability affected the following Cisco
products if they were running a vulnerable release of Cisco software:
3000 Series Industrial Security Appliances (ISAs)
Firepower Threat Defense (FTD) Software
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. If the UTD file is not installed, the device is not vulnerable.
1000 Series Integrated Services Routers (ISRs)
4000 Series Integrated Services Routers (ISRs)
Cloud Services Router 1000V
Integrated Services Virtual Router (ISRv)
For information about which Cisco software releases are vulnerable, 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
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, Cisco Firepower Threat Defense (FTD) releases
6.5.0.5 and later contained the fix for this vulnerability.
At the time of publication, Cisco UTD Snort IPS Engine Software for IOS XE
17.4.1 ^ 1 contained the fix for this vulnerability.
At the time of publication, the open source Snort project release 2.9.14.10
and later contained the fix for this vulnerability. For more information,
see the Snort website .
See the Details section in the bug ID(s) at the top of this advisory for
the most complete and current information.
1. Starting in 17.2.1, IOS XE and IOS XE SD-WAN use the same image file.
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.
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort-app-bypass-cSBYCATq
Revision History
o +---------+---------------------------+------------+--------+-------------+
| Version | Description | Section | Status | Date |
+---------+---------------------------+------------+--------+-------------+
| | Updated vulnerability | Vulnerable | | |
| 1.1 | information for Cisco UTD | Products | Final | 2021-NOV-12 |
| | Engine requirements. | | | |
+---------+---------------------------+------------+--------+-------------+
| 1.0 | Initial public release. | - | Final | 2021-JAN-13 |
+---------+---------------------------+------------+--------+-------------+
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