Cisco Security Advisory
ConfD CLI Secure Shell Server Privilege Escalation Vulnerability
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CVSS:3.1/AV:L/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 ConfD could allow an authenticated, local attacker to execute arbitrary commands at the level of the account under which ConfD is running, which is commonly root. To exploit this vulnerability, an attacker must have a valid account on the 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 ConfD built-in Secure Shell (SSH) server for CLI was enabled. If the ConfD 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 ConfD is running, which is commonly root.
Note: Any user who can authenticate to the built-in SSH server may exploit this vulnerability. By default, all ConfD users have this access if the server is enabled.
Software updates that address this vulnerability have been released. 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-confd-priv-esc-LsGtCRx4
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Vulnerable Products
This vulnerability affects the following releases of ConfD if the built-in SSH server for CLI is enabled:
- Releases 7.4 through 7.4.3
- Releases 7.5 through 7.5.2
- Releases 7.6 through 7.6.14
- Releases 7.7 through 7.7.12
- Releases 7.8 through 7.8.10
- Releases 8.0 through 8.0.7
- Releases 8.1 through 8.1.3
To determine whether the built-in SSH server is enabled, see Section 4.1.1, “Disable built-in support for SSH in ConfD,” in the ConfD and High Security Applications V2 application note.
Products 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 are no workarounds that address this vulnerability. However, a mitigation is available.
Administrators can disable the ConfD built-in SSH server and use an external SSH server such as OpenSSH. For guidance on disabling the built-in support of SSH in ConfD, see Section 4.1.1, “Disable built-in support for SSH in ConfD,” in the ConfD and High Security Applications V2 application note.
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.
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Tail-f, a Cisco company, has released 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 a current license and have a valid support and maintenance agreement. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of their license agreement with Tail-f Systems AB. Security software updates do not entitle customers to a new software license or additional software feature sets.
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.
Customers who have a current license and have a valid support and maintenance agreement can download the fixed version of software from their existing Tail-f delivery server download account.
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 open a support ticket in the Tail-f Support system.
Fixed Releases
In the following table, the left column lists ConfD 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.
ConfD Release First Fixed Release 7.4 7.4.3.1 7.5 7.5.2.1 7.6 7.6.14.1 7.7 7.7.13 7.8 7.8.11 8.0 8.0.8 8.1 8.1.4 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 not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
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This vulnerability was found during the resolution of a Cisco TAC support case.
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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 2.0 Updated information about vulnerable releases and fixed releases. Vulnerable Products and Fixed Releases Final 2023-OCT-04 1.0 Initial public release. - Final 2021-AUG-04
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