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             AUSCERT External Security Bulletin Redistribution

          Cisco IOS XE Software for Cisco Catalyst Switches IPv4
                      Denial of Service Vulnerability
                               29 March 2018


        AusCERT Security Bulletin Summary

Product:           Cisco Catalyst 3850
                   Cisco Catalyst 3650
Publisher:         Cisco Systems
Operating System:  Cisco
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2018-0177  

Original Bulletin: 

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Cisco Security Advisory

Cisco IOS XE Software for Cisco Catalyst Switches IPv4 Denial of Service


Advisory ID:     cisco-sa-20180328-ipv4

First Published: 2018 March 28 16:00 GMT

Version 1.0:     Final

Workarounds:     No workarounds available

Cisco Bug IDs:



CVSS Score:


  o A vulnerability in the IP Version 4 (IPv4) processing code of Cisco IOS XE
    Software running on Cisco Catalyst 3850 and Cisco Catalyst 3650 Series
    Switches could allow an unauthenticated, remote attacker to cause high CPU
    utilization, traceback messages, or a reload of an affected device that
    leads to a denial of service (DoS) condition.

    The vulnerability is due to incorrect processing of certain IPv4 packets.
    An attacker could exploit this vulnerability by sending specific IPv4
    packets to an IPv4 address on an affected device. A successful exploit
    could allow the attacker to cause high CPU utilization, traceback messages,
    or a reload of the affected device that leads to a DoS condition. If the
    switch does not reboot when under attack, it would require manual
    intervention to reload the device.

    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:

    This advisory is part of the March 28, 2018, release of the Cisco IOS and
    IOS XE Software Security Advisory Bundled Publication, which includes 20
    Cisco Security Advisories that describe 22 vulnerabilities. For a complete
    list of the advisories and links to them, see Cisco Event Response: March
    2018 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled

Affected Products

  o Vulnerable Products

    This vulnerability affects Cisco Catalyst 3850 and Cisco Catalyst 3650
    Series Switches that are running Cisco IOS XE Software Release 16.1.1 or
    later, until the first fixed release, and are configured with an IPv4

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

    Determining the Cisco IOS XE Software Release

    To determine which Cisco IOS XE Software release is running on a device,
    administrators can log in to the device, use the show version command in
    the CLI, and then refer to the system banner that appears. If the device is
    running Cisco IOS XE Software, the system banner displays Cisco IOS
    Software, Cisco IOS XE Software, or similar text.

    The following example shows the output of the command for a device that is
    running Cisco IOS XE Software Release 16.2.1 and has an installed image
    name of CAT3K_CAA-UNIVERSALK9-M:

        ios-xe-device# show version

        Cisco IOS Software, Catalyst L3 Switch Software (CAT3K_CAA-UNIVERSALK9-M), Version Denali 16.2.1, RELEASE SOFTWARE (fc1)
        Technical Support: http://www.cisco.com/techsupport
        Copyright (c) 1986-2016 by Cisco Systems, Inc.
        Compiled Sun 27-Mar-16 21:47 by mcpre

    For information about the naming and numbering conventions for Cisco IOS XE
    Software releases, see the Cisco IOS and NX-OS Software Reference Guide.

    Products Confirmed Not Vulnerable

    No other Cisco products are currently known to be affected by this

    Cisco has confirmed that this vulnerability does not affect Cisco IOS
    Software, Cisco IOS XR Software, or Cisco NX-OS Software.


  o This vulnerability is triggered by certain IPv4 packets that are sent to an
    affected device. The same IPv4 packets that are sent through the device do
    not trigger this vulnerability.

Indicators of Compromise

  o If an exploit has occurred, the device CPU usage will be high, as shown by
    the show process cpu sorted CLI command. Depending on the CPU usage, this
    information may be available only from a console connection, as remote VTY
    sessions may not be possible. Specifically, the IOSXE-RP Punt Se process
    will be the one that is consuming the CPU, as shown in the following

        Cat3850# show process cpu sorted | ex 0.00

        CPU utilization for five seconds: 96%/66%; one minute: 61%; five minutes: 20%
         PID Runtime(ms)     Invoked      uSecs   5Sec   1Min   5Min TTY Process
         117       21796       90021        242 40.19% 21.51%  6.27%   0 IOSXE-RP Punt Se
         203         153        6311         24  0.07%  0.04%  0.02%   0 IP ARP Retry Age
          73        3448        1141       3021  0.07%  0.24%  0.55%   0 IOSD ipc task
         200         174        6311         27  0.07%  0.05%  0.04%   0 IPAM Manager


  o There are no workarounds that address this vulnerability.

    If the device has high CPU usage for the IOSXE-RP Punt Se process, try to
    identify the source of the IP traffic and prevent that address from sending
    the packets to the affected device, by either filtering the source address
    or removing the source device from the network.

    To recover the device, shut down the interface that the IPv4 packets are
    being received on, eliminate the source of the attack via an infrastructure
    access control list or other methods, and re-enable the interface.

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 and Alerts 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:

    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

    This vulnerability is fixed in Cisco IOS XE Software Releases Denali
    16.3.4, Everest 16.5.1a, Everest 16.5.2, Everest 16.6.1, and later.

    Cisco IOS and IOS XE Software

    To help customers determine their exposure to vulnerabilities in Cisco IOS
    and IOS XE Software, Cisco provides a tool, the Cisco IOS Software Checker,
    that identifies any Cisco Security Advisories that impact a specific
    software release and the earliest release that fixes the vulnerabilities
    described in each advisory ("First Fixed"). If applicable, the tool also
    returns the earliest release that fixes all the vulnerabilities described
    in all the advisories identified ("Combined First Fixed").

    Customers can use this tool to perform the following tasks:

       Initiate a search by choosing one or more releases from a drop-down
        list or uploading a file from a local system for the tool to parse
       Enter the output of the show version command for the tool to parse
       Create a custom search by including all previously published Cisco
        Security Advisories, a specific advisory, or all advisories in the most
        recent bundled publication

    To determine whether a release is affected by any published Cisco Security
    Advisory, use the Cisco IOS Software Checker on Cisco.com or enter a
    Cisco IOS Software or Cisco IOS XE Software release--for example, 15.1(4)M2
    or 3.13.8S--in the following field:

    [                    ] [Check]

    For a mapping of Cisco IOS XE Software releases to Cisco IOS Software
    releases, refer to the Cisco IOS XE 2 Release Notes, Cisco IOS XE 3S
    Release Notes, or Cisco IOS XE 3SG Release Notes, depending on the
    Cisco IOS XE Software release.

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.

Subscribe to Cisco Security Notifications

  o Subscribe

Related to This Advisory

  o Cisco Event Response: March 2018 Semiannual Cisco IOS and IOS XE Software
    Security Advisory Bundled Publication
    Cisco Security Blog: Cisco IOS and IOS XE Software Bundled Publication
    March 2018


  o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-ipv4

Revision History

    | Version  |        Description         | Section  | Status  |      Date      |
    | 1.0      | Initial public release.    | --       | Final   | 2018-March-28  |

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