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             AUSCERT External Security Bulletin Redistribution

        Multiple Cisco Products Snort Ethernet Frame Decoder Denial
                         of Service Vulnerability
                               4 March 2021


        AusCERT Security Bulletin Summary

Product:           Cisco Products
Publisher:         Cisco Systems
Operating System:  Cisco
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2021-1285  

Original Bulletin: 

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

Multiple Cisco Products Snort Ethernet Frame Decoder Denial of Service

Priority:        High
Advisory ID:     cisco-sa-snort-ethernet-dos-HGXgJH8n
First Published: 2021 March 3 16:00 GMT
Version 1.0:     Final
Workarounds:     No workarounds available
Cisco Bug IDs:   CSCvu88170
CVE Names:       CVE-2021-1285
CWEs:            CWE-770

CVSS Score:


  o Multiple Cisco products are affected by a vulnerability in the Ethernet
    Frame Decoder of the Snort detection engine that could allow an
    unauthenticated, adjacent attacker to cause a denial of service (DoS)

    The vulnerability is due to improper handling of error conditions when
    processing Ethernet frames. An attacker could exploit this vulnerability by
    sending malicious Ethernet frames through an affected device. A successful
    exploit could allow the attacker to exhaust disk space on the affected
    device, which could result in administrators being unable to log in to the
    device or the device being unable to boot up correctly.

    Note: Manual intervention is required to recover from this situation.
    Customers are advised to contact the Cisco Technical Assistance Center
    (TAC) to help recover a device in this 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:

Affected Products

  o Vulnerable Products

    This vulnerability affects all open source Snort project releases earlier
    than Release 2.9.17. For more information on open source Snort, see the
    Snort website .

    Impact to Cisco Products

    This vulnerability affects the following Cisco products, if they are
    running a vulnerable release of Cisco UTD Snort IPS Engine Software for IOS
    XE or Cisco UTD Engine for IOS XE SD-WAN Software and are configured to
    pass Ethernet frames to the Snort detection engine:

       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 Router 1000V Series
       Integrated Services Virtual Router (ISRv)

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

    Products Confirmed Not Vulnerable

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

       3000 Series Industrial Security Appliances (ISAs)
       Adaptive Security Appliance (ASA) Software
       Catalyst 8500 Series Edge Platforms
       Catalyst 8500L Series Edge Platforms
       Firepower Management Center (FMC) Software
       Firepower Threat Defense (FTD) Software ^ 1
       Meraki Security Appliances

    1. A related vulnerability affecting Cisco FTD Software was previously
    resolved and disclosed as Cisco Firepower Threat Defense Software Inline
    Pair/Passive Mode Denial of Service Vulnerability .


  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:

    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

    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

    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

    Fixed Releases

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

    Cisco IOS XE Software and Cisco IOS XE SD-WAN Software

    Cisco UTD Snort IPS Engine Software for  First Fixed Release for This
    IOS XE and                               Vulnerability
    Cisco UTD Engine for IOS XE SD-WAN
    Software ^1
    Earlier than 16.12                       Migrate to a fixed release.
    16.12                                    16.12.5
    17.1                                     Migrate to a fixed release.
    17.2                                     Migrate to a fixed release.
    17.3                                     17.3.3
    17.4                                     17.4.1a

    1. Starting with release 17.2.1, Cisco IOS XE Software and Cisco IOS XE
    SD-WAN Software share the same image file.

    Open Source Snort

    The open source Snort project versions 2.9.17 and later contain the fix for
    this vulnerability. For more information on open source Snort, see the
    Snort website .

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.


  o This vulnerability was found during the resolution of a Cisco TAC support

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.


  o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort-ethernet-dos-HGXgJH8n

Revision History

  o +----------+---------------------------+----------+--------+--------------+
    | Version  |        Description        | Section  | Status |     Date     |
    | 1.0      | Initial public release.   | -        | Final  | 2021-MAR-03  |

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