Cisco FXOS and NX-OS Software Simple Network Management Protocol Denial of Service Vulnerability

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Updated:July 12, 2021
Document ID:1557939468281774

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Cisco Security Advisory

Cisco FXOS and NX-OS Software Simple Network Management Protocol Denial of Service Vulnerability

High
Advisory ID:
cisco-sa-20190515-nxos-snmp-dos
First Published:
2019 May 15 16:00 GMT
Last Updated: 
2021 July 12 14:24 GMT
Version 1.3:
Final
Workarounds:
No workarounds available
CVE-2019-1858
CWE-755
CVSS Score:
Base 8.6Click Icon to Copy Verbose Score
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X
CVE-2019-1858
CWE-755

Summary

  • A vulnerability in the Simple Network Management Protocol (SNMP) input packet processor of Cisco FXOS Software and Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause the SNMP application to leak system memory, which could cause an affected device to restart unexpectedly.

    The vulnerability is due to improper error handling when processing inbound SNMP packets. An attacker could exploit this vulnerability by sending multiple crafted SNMP packets to an affected device. A successful exploit could allow the attacker to cause the SNMP application to leak system memory because of an improperly handled error condition during packet processing. Over time, this memory leak could cause the SNMP application to restart multiple times, leading to a system-level restart and a denial of service (DoS) 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:
    https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190515-nxos-snmp-dos

Affected Products

  • Vulnerable Products

    This vulnerability affects the following Cisco products if they are running a vulnerable release of Cisco FXOS or NX-OS Software:

    • Firepower 4100 Series
    • Firepower 9300 Security Appliances
    • MDS 9000 Series Multilayer Switches
    • Nexus 1000V Switch for Microsoft Hyper-V
    • Nexus 1000V Switch for VMware vSphere
    • Nexus 3000 Series Switches
    • Nexus 3500 Platform Switches
    • Nexus 5500 Platform Switches
    • Nexus 5600 Platform Switches
    • Nexus 6000 Series Switches
    • Nexus 7000 Series Switches
    • Nexus 7700 Series Switches
    • Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) mode
    • Nexus 9000 Series Switches in standalone NX-OS mode
    • Nexus 9500 R-Series Switching Platform

    Determining the Status of SNMP

    Administrators can determine whether SNMP is running on a device by using the show running-config snmp command in the device CLI. If the command returns output, SNMP is configured.

    nxos-switch# show running-config snmp
    .
    .
    .
    
snmp-server user admin network-admin auth md5 ***** priv ***** localizedkey
    snmp-server community community-string group network-admin

    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:

    • Firepower 2100 Series
    • Nexus 3600 Platform Switches
    • UCS 6200 Series Fabric Interconnects
    • UCS 6300 Series Fabric Interconnects
    • UCS 6400 Series Fabric Interconnects

Details

  • SNMP is an application-layer protocol that provides a standardized framework and a common language for monitoring and managing devices in a network. It defines a message format for communication between SNMP managers and agents.

    An SNMP agent gathers data from the SNMP MIB, which is the repository of information about device parameters and network data. It also responds to requests from an SNMP manager to get or set data. An SNMP agent contains MIB variables for which values can be requested or changed by an SNMP manager by using get or set operations.

    This vulnerability affects all versions of SNMP supported on the device—Versions 1, 2c, and 3. An attacker could exploit this vulnerability by sending a specific SNMP packet to an affected device via IPv4 or IPv6. Only traffic directed to the affected system can be used to exploit this vulnerability.

    To exploit this vulnerability, the attacker does not always require valid SNMP credentials for the affected system.

Workarounds

  • There are no workarounds that address this vulnerability.

    As a mitigation for the vulnerability that is described in this advisory, administrators can configure an access control list (ACL) on an SNMP community to filter incoming SNMP requests to ensure that SNMP polling is performed only by trusted SNMP clients. In the following example, the device will accept incoming SNMP requests only from a single trusted host, 192.168.1.2:

    switch# show access-list acl_for_snmp
    IPV4 ACL acl_for_snmp
      10 permit udp 192.168.1.2/32 192.168.1.3/32 eq snmp

    To implement the preceding ACL, administrators can add it to the snmp-server community configuration command:

    switch# show running-config snmp
    !Command: show running-config snmp
    snmp-server community mycompany
     use-acl acl_for_snmp

    For additional information about configuring ACLs to filter incoming SNMP requests, see Filtering SNMP Requests in the NX-OS Configuration Guide.

Fixed Software

  • Cisco has released free software updates that address the vulnerabilities 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 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 providers.

    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

    No upgrade action is necessary for products that are running Cisco NX-OS Software for cases in which customers have already applied a recommended Cisco NX-OS Software release to address the March 2019 Cisco FXOS and NX-OS Software bundle. See Cisco Event Response: March 2019 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication for a list of advisories in the bundle.

    Customers who have not applied a recommended release to address the March 2019 bundle or who have devices that are running Cisco FXOS software are advised to upgrade to an appropriate release as indicated in the applicable table in this section. In the following tables, the left column lists Cisco FXOS and NX-OS Software releases. The right column indicates the first release that includes the fix for this vulnerability.

    Firepower 4100 Series and Firepower 9300 Security Appliances: CSCvn19468

    Cisco FXOS Software Release First Fixed Release for This Vulnerability
    Prior 2.2 2.2.2.91
    2.2 2.2.2.91
    2.3 2.3.1.130
    2.4 2.4.1.222
    2.6 2.6.1.131

    MDS 9000 Series Multilayer Switches: CSCvc58707

    Cisco NX-OS Software Release First Fixed Release for This Vulnerability
    5.2 6.2(29)
    6.2 6.2(29)
    8.1 8.1(1)
    8.2 Not vulnerable
    8.3 Not vulnerable

    Nexus 1000V Switch for Microsoft Hyper-V: CSCvn19483

    Cisco NX-OS Software Release First Fixed Release for This Vulnerability
    Prior to 5.2 5.2(1)SM3(2.1)
    5.2 5.2(1)SM3(2.1)

    Nexus 1000V Switch for VMware vSphere: CSCvn19463

    Cisco NX-OS Software Release First Fixed Release for This Vulnerability
    Prior to 5.2 5.2(1)SV3(4.1a)
    5.2 5.2(1)SV3(4.1a)

    Nexus 3000 Series Switches and Nexus 9000 Series Switches in Standalone NX-OS Mode: CSCvd45657

    Cisco NX-OS Software Release First Fixed Release for This Vulnerability
    Prior to 7.0(3)I4 7.0(3)I4(8)
    7.0(3)I4 7.0(3)I4(8)
    7.0(3)I7 7.0(3)I7(2)
    9.2(1) Not vulnerable

    Nexus 3500 Platform Switches: CSCvn19464

    Cisco NX-OS Software Release First Fixed Release for This Vulnerability
    Prior to 6.0(2)A8 6.0(2)A8(4)
    6.0(2)A8 6.0(2)A8(4)
    7.0(3)I7 7.0(3)I7(2)
    9.2 Not vulnerable

    Nexus 5500, 5600, and 6000 Series Switches: CSCvn19465

    Cisco NX-OS Software Release First Fixed Release for This Vulnerability
    Prior to 7.1 7.1(5)N1(1b)
    7.1 7.1(5)N1(1b)
    7.3 7.3(4)N1(1a)

    Nexus 7000 and 7700 Series Switches: CSCvc58707

    Cisco NX-OS Software Release First Fixed Release for This Vulnerability
    Prior to 6.2 6.2(22)
    6.2 6.2(22)
    7.2 7.2(0)D1(1)
    7.3 Not vulnerable
    8.0 8.1(1)
    8.1 Not vulnerable
    8.2 Not vulnerable
    8.3 Not vulnerable

    Nexus 9000 Series Fabric Switches in ACI Mode: CSCvn19457

    Cisco NX-OS Software Release First Fixed Release for This Vulnerability
    Prior to 13.1 14.0(2c)
    13.1 14.0(2c)
    13.2 14.0(2c)
    14.0 14.0(2c)
    14.1 14.1(1i)

    Nexus 9500 R-Series Switching Platform: CSCvd45657

    Cisco NX-OS Software Release First Fixed Release for This Vulnerability
    7.0(3) 7.0(3)F3(1)
    9.2 Not vulnerable


    Additional Resources

    For help determining the best Cisco NX-OS Software release for a Cisco Nexus Switch, administrators can refer to the following Recommended Releases documents. If a security advisory recommends a later release, Cisco recommends following the advisory guidance.

    Cisco MDS Series Switches
    Cisco Nexus 1000V for VMware Switch
    Cisco Nexus 3000 Series and 3500 Series Switches
    Cisco Nexus 5000 Series Switches
    Cisco Nexus 5500 Platform Switches
    Cisco Nexus 6000 Series Switches
    Cisco Nexus 7000 Series Switches
    Cisco Nexus 9000 Series Switches
    Cisco Nexus 9000 Series ACI-Mode Switches

    For help determining the best Cisco NX-OS Software release for Cisco UCS, refer to the Recommended Releases documents in the release notes for the device.

Exploitation and Public Announcements

  • 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

  • This vulnerability was found during internal security testing.

Cisco Security Vulnerability Policy

  • 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.

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Revision History

  • Version Description Section Status Date
    1.3 Updated the fixed release information for MDS 9000 Series Multilayer Switches. Fixed Software Final 2021-JUL-12
    1.2 Corrected errors in the Fixed Release tables for MDS and N7K. Fixed Software Final 2019-MAY-20
    1.1 Added mitigation. Workarounds Final 2019-MAY-16
    1.0 Initial public release. — Final 2019-MAY-15
    Show Less

Cisco Security Vulnerability Policy

  • 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

Related to This Advisory