Cisco Security Advisory
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CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:X/RL:X/RC:X
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A vulnerability in the key-based SSH authentication feature of Cisco StarOS Software could allow an authenticated, remote attacker to elevate privileges on an affected device.
This vulnerability is due to insufficient validation of user-supplied credentials. An attacker could exploit this vulnerability by sending a valid low-privileged SSH key to an affected device from a host that has an IP address that is configured as the source for a high-privileged user account. A successful exploit could allow the attacker to log in to the affected device through SSH as a high-privileged user.
Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability.
This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-staros-ssh-privesc-BmWeJC3h
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Vulnerable Products
This vulnerability affects the following Cisco products if they are running a vulnerable release of Cisco StarOS Software and are configured for key-based SSH authentication for multiple usernames that share the same IP address:
- ASR 5000 Series Routers
- Virtualized Packet Core - Distributed Instance (VPC-DI)
- Virtualized Packet Core - Single Instance (VPC-SI)
For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.
Determine Whether a Device is Affected
To determine if a device is affected by this vulnerability, look for the authorized-key command in the server sshd configuration. A device is affected by this vulnerability if there are two or more instances of the command with the same IP address configured on the host parameter, as in the following example:
[local]host_name(config-sshd)# authorized-key username Administrator1 host 192.168.1.1
[local]host_name(config-sshd)# authorized-key username Operator1 host 192.168.1.1Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.
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There is a workaround that addresses this vulnerability. To remove the attack vector for this vulnerability, user accounts configured for SSH key-based authentication must each use a different IP address.
While this workaround 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.
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Cisco has released free software updates that address the vulnerability described in this advisory. Customers with service contracts that entitle them to regular software updates should obtain security fixes through their usual update channels.
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.htmlAdditionally, 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.
The Cisco Support and Downloads page on Cisco.com provides information about licensing and downloads. This page can also display customer device support coverage for customers who use the My Devices tool.
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
In the following table, the left column lists Cisco software releases. The right column indicates whether a release is affected by the vulnerability that is described in this advisory and the first release that includes the fix for this vulnerability. Customers are advised to upgrade to an appropriate fixed software release as indicated in this section.
Cisco StarOS Software Release First Fixed Release Earlier than 21.22 Migrate to a fixed release. 21.22 21.22.14 21.22.n 21.22.n14 21.23 21.23.31 21.23.n 21.23.n12 21.24 Fix planned for May 2023. 21.25 21.25.15 21.26 21.26.17 21.27 21.27.6 21.27.m 21.27.m1 21.28 21.28.3 21.28.m 21.28.m4 The Cisco Product Security Incident Response Team (PSIRT) validates only the affected and fixed release information that is documented in this advisory.
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The Cisco PSIRT is aware that proof-of-concept exploit code is available for the vulnerability described in this advisory.
The Cisco PSIRT is not aware of any malicious use of the vulnerability that is described in this advisory.
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Cisco would like to thank Adrien Mourier and Orange CERT-CC of Orange for reporting this vulnerability.
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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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Show LessVersion Description Section Status Date 1.0 Initial public release. — Final 2023-APR-19
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