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             AUSCERT External Security Bulletin Redistribution

                               ESB-2021.0140
        Multiple Cisco Products Snort Application Detection Engine
                        Policy Bypass Vulnerability
                              14 January 2021

===========================================================================

        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

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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
Version 1.0:     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 the following Cisco
    products if they were running a vulnerable software release:

       1000 Series Integrated Services Routers (ISRs)
       3000 Series Industrial Security Appliances (ISAs)
       4000 Series Integrated Services Routers (ISRs)
       Cloud Services Router 1000V
       Firepower Threat Defense (FTD) Software
       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.

    This vulnerability also affected all open source Snort project releases
    earlier than Release 2.9.14. For more information, see the Snort website .

    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     |
    +----------+---------------------------+----------+--------+--------------+
    | 1.0      | Initial public release.   | -        | Final  | 2021-JAN-13  |
    +----------+---------------------------+----------+--------+--------------+

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