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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2021.1039 Network Convergence System 520 Routers Denial of Service Vulnerability 25 March 2021 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Cisco IOS XE Software for Network Convergence System 520 Routers Publisher: Cisco Systems Operating System: Cisco Impact/Access: Denial of Service -- Remote/Unauthenticated Resolution: Patch/Upgrade CVE Names: CVE-2021-1394 Original Bulletin: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ncs520-tcp-ZpzzOxB - --------------------------BEGIN INCLUDED TEXT-------------------- Cisco IOS XE Software for Network Convergence System 520 Routers Denial of Service Vulnerability Priority: Medium Advisory ID: cisco-sa-ncs520-tcp-ZpzzOxB First Published: 2021 March 24 16:00 GMT Version 1.0: Final Workarounds: No workarounds available Cisco Bug IDs: CSCvm96192 CVE Names: CVE-2021-1394 CWEs: CWE-399 Summary o A vulnerability in the ingress traffic manager of Cisco IOS XE Software for Cisco Network Convergence System (NCS) 520 Routers could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition in the web management interface of an affected device. This vulnerability is due to incorrect processing of certain IPv4 TCP traffic that is destined to an affected device. An attacker could exploit this vulnerability by sending a large number of crafted TCP packets to the affected device. A successful exploit could allow the attacker to cause the web management interface to become unavailable, resulting in a DoS condition. Note: This vulnerability does not impact traffic that is going through the device or going to the Management Ethernet interface of 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: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ncs520-tcp-ZpzzOxB Affected Products o Vulnerable Products At the time of publication, this vulnerability affected Cisco NCS 520 Routers if they were running a vulnerable release of Cisco IOS XE Software and had the HTTP server enabled. For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory. Determine the HTTP Server Configuration To determine whether the HTTP Server feature is enabled for a device, log in to the device and use the show running-config | include ip http server| secure|active command in the CLI to check for the presence of the ip http server command or the ip http secure-server command in the global configuration. If either command is present and configured, the HTTP Server feature is enabled for the device. The following example shows the output of the show running-config | include ip http server|secure|active command for a device that has the HTTP Server feature enabled: Router# show running-config | include ip http server|secure|active ip http server ip http secure-server Note: The presence of either command or both commands in the device configuration indicates that the web UI feature is enabled. If the ip http server command is present and the configuration also contains ip http active-session-modules none , the vulnerability is not exploitable over HTTP. If the ip http secure-server command is present and the configuration also contains ip http secure-active-session-modules none , the vulnerability is not exploitable over HTTPS. 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: IOS Software IOS XR Software NX-OS Software 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. Cisco IOS and IOS XE Software To help customers determine their exposure to vulnerabilities in Cisco IOS and IOS XE Software, Cisco provides the Cisco Software Checker to identify 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 the Cisco Software Checker to search advisories in the following ways: Choose the software and one or more releases Upload a .txt file that includes a list of specific releases Enter the output of the show version command After initiating a search, customers can customize the search to include all Cisco Security Advisories, a specific advisory, or all advisories in the most recent bundled publication. Customers can also use the following form to determine whether a release is affected by any Cisco Security Advisory by entering a Cisco IOS or IOS XE Software release-for example, 15.1(4)M2 or 3.13.8S. By default, the Cisco Software Checker includes results only for vulnerabilities that have a Critical or High Security Impact Rating (SIR). To include results for Medium SIR vulnerabilities, customers can use the Cisco Software Checker on Cisco.com and check the Medium check box in the drop-down list under Impact Rating when customizing a search. 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. Source o This vulnerability was found during internal security testing. 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-ncs520-tcp-ZpzzOxB Revision History o +----------+---------------------------+----------+--------+--------------+ | Version | Description | Section | Status | Date | +----------+---------------------------+----------+--------+--------------+ | 1.0 | Initial public release. | - | Final | 2021-MAR-24 | +----------+---------------------------+----------+--------+--------------+ - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. AusCERT takes no responsibility for consequences which may arise from following or acting on information or advice contained in this security bulletin. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: https://www.auscert.org.au/bulletins/ =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQIVAwUBYFwEkeNLKJtyKPYoAQisqw//QkqNu37gTpGrdDw9mFEUh3FktMDhI6as ZNqV8cR8mYPvPFFBrgLBfVds26lO83VefwCznQjaBgqiuZDIcGlj+1eeqNwh1zI6 gXYc1Zno7cN7TTFQ2u+e5Lw77z5mQJkmkGHmOGEdjUv3tfLf4sjq+3rYDtLUExve cHBsFiAQbIv8j42kAJg1PFCcBqFJcUCf0a6XAuL6PjrNwWlq1zX7uDMvng/to89b lR5RVh9ohRdcIare69rdGxPBumlV4NA8oWQsq2TJzHWf/6ODx0jzRLM50NUE0W1b h8DsD7OfjkLtPNvHdNUyuyswWZFZK/OdsSeeSnMwiM24O9mhOlq9+s7m88xckECJ mB4sXA53zCnmVln3ROUPgetAIzNo5vKOD1gNm/QLt8jeghCKWj2cYoA/TUGytp8O Vt/DtSFmiuldKpJRUCZ6mpByzqj9YjWVQfpYg7mT3I6+upvOKvHoPF6RaDXIaPo3 xDI/sMFi15Cg0p4evRCGM0nfDFL0oGKYEUtPSKrmDb6M48Vspt5GkVKAVDtc2Sn6 +dOHeTjzBLEgcrqJYQuB+vUpcj/EVUJWSWevZO9L1TfO3UMBHkQWBgac57V4vXSj epMYq97U3F1TBKfLqpU8uPVnAkD6Ehr6XpLd966oqZ50pAjPSzkzOzwxxzOpINnt mAir2at2Hr8= =cIks -----END PGP SIGNATURE-----