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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2021.2631 Cisco Network Services Orchestrator CLI Secure Shell Server Privilege Escalation Vulnerability 5 August 2021 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Cisco Network Services Orchestrator (NSO) Publisher: Cisco Systems Operating System: Cisco Impact/Access: Execute Arbitrary Code/Commands -- Existing Account Increased Privileges -- Existing Account Resolution: Patch/Upgrade CVE Names: CVE-2021-1572 Original Bulletin: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nso-priv-esc-XXqRtTfT - --------------------------BEGIN INCLUDED TEXT-------------------- Cisco Network Services Orchestrator CLI Secure Shell Server Privilege Escalation Vulnerability Priority: High Advisory ID: cisco-sa-nso-priv-esc-XXqRtTfT First Published: 2021 August 4 16:00 GMT Version 1.0: Final Workarounds: No workarounds available Cisco Bug IDs: CSCvy36721 CVE Names: CVE-2021-1572 CWEs: CWE-266 Summary o A vulnerability in Cisco Network Services Orchestrator (NSO) could allow an authenticated, local attacker to execute arbitrary commands at the level of the account under which Cisco NSO is running, which is root by default. To exploit this vulnerability, an attacker must have a valid account on an affected device. The vulnerability exists because the affected software incorrectly runs the SFTP user service at the privilege level of the account that was running when the NSO built-in Secure Shell (SSH) server for CLI was enabled. If the NSO built-in SSH server was not enabled, the device is not affected by this vulnerability. An attacker with low-level privileges could exploit this vulnerability by authenticating to an affected device and issuing a series of commands at the SFTP interface. A successful exploit could allow the attacker to elevate privileges to the level of the account under which Cisco NSO is running, which is root by default. Note: Any user who can authenticate to the built-in SSH server may exploit this vulnerability. By default, all Cisco NSO users have this access if the server is enabled. 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-nso-priv-esc-XXqRtTfT Affected Products o Vulnerable Products This vulnerability affects the following releases of Cisco NSO if the NSO built-in SSH server for CLI is enabled: Releases 5.4 through 5.4.3.1 Releases 5.5 through 5.5.2.2 The NSO built-in SSH server is disabled by default in an NSO system installation. To determine whether the built-in SSH server is enabled, navigate to the ncs.conf file, which is usually located under the /etc/ncs directory. The built-in SSH server is enabled if the value for SSH enabled is true , as shown in this example: <cli> <enabled>true</enabled> <!-- Use the builtin SSH server --> <ssh> <enabled>true</enabled> <ip>0.0.0.0</ip> <port>2024</port> </ssh> </cli> Products Confirmed Not Vulnerable Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability. Workarounds o There are no workarounds that address this vulnerability. However, a mitigation is available. Administrators can disable the NSO built-in SSH server and run the ncs_cli program as a login shell. For guidance on using the ncs_cli program, see NSO 5.5 User Guide: Starting the CLI . While this mitigation has been deployed and was proven successful in a test environment, customers should determine the applicability and effectiveness in their own environment and under their own use conditions. Customers should be aware that any workaround or mitigation that is implemented may negatively impact the functionality or performance of their network based on intrinsic customer deployment scenarios and limitations. Customers should not deploy any workarounds or mitigations before first evaluating the applicability to their own environment and any impact to such environment. 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: 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 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 Cisco fixed this vulnerability in Cisco NSO releases 5.4.3.2 and later and releases 5.5.2.3 and later. 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-nso-priv-esc-XXqRtTfT Revision History o +----------+---------------------------+----------+--------+--------------+ | Version | Description | Section | Status | Date | +----------+---------------------------+----------+--------+--------------+ | 1.0 | Initial public release. | - | Final | 2021-AUG-04 | +----------+---------------------------+----------+--------+--------------+ - --------------------------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 iQIVAwUBYQs/KONLKJtyKPYoAQjOaA/+P6aA+By+9/DO6joxLU7zP6OI2ar5ltFm dgQOA7QcYYEBn78pBffhLiw0Rx3iOdk2DNECl9DqdKkywkDtFNmowWIqzwbin+TM hUoFVJVqxYsrkg5dF8qqUrnHUcRyfH9cN8aUHdXzY4KP9QHTXGS9WgG6RRo9NLYW d1mLyaUTYzt+S1xltQsOdIaXglInLZEEuyKIYkjEKcoFZ8w73muzmg5ECEHf9dWc /hrzEnsflfORc6bkJ3/w51HIoH+Gu6Kw8ah5bp1Heb6KqSCO+3Ufy+5thsISUoyJ 3Vm43LmH3S4hS/E7c4y7fKOtZyLW6zGo2U6+XQDkclAnoIbVIUt1Ah/ti7v9rhku 2ocpAu0QRYfd7LDm2VDLMOwjlRNzXo1llFTSXkkKQM69zUqv6Xi/jr1ZyPxkOL2W n8sUc2wI52myToPj2V3W9sH0xijXG2gspOZOZLBxeVx5artYLHNDqBGf8LfP+hsh oAmaoNw6RLwV+Q/sKi2tnuxt5LRuaYB2X+1nVTCihvM3vETfo0W4ED85jUe0NaiI 9MrBHu7AILLXavwkGiWgHPyahJEazsLkXLTiRwlUcC2JcmsygjYCSy2cUKdf3/zx a9Kd4i0dDTOuIsmXIpiuGEP/UeW1S44+hTjcXUZ2n+UO9PBO/s3kEKq/qBUKEVWx wujsYpVkeuE= =3uv7 -----END PGP SIGNATURE-----