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
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
This vulnerability affects the following releases of Cisco NSO if the NSO built-in SSH server for CLI is enabled:
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>
Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.
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.
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 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.
Cisco fixed this vulnerability in Cisco NSO releases 5.4.3.2 and later and releases 5.5.2.3 and later.
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.
This vulnerability was found during the resolution of a Cisco TAC support case.
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.
| Version | Description | Section | Status | Date |
|---|---|---|---|---|
| 1.0 | Initial public release. | - | Final | 2021-AUG-04 |
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.
A standalone copy or paraphrase of the text of this document that omits the distribution URL is an uncontrolled copy and may lack important information or contain factual errors. The information in this document is intended for end users of Cisco products.
Vulmon