Headline
CVE-2021-1572: Cisco Security Advisory: ConfD CLI Secure Shell Server Privilege Escalation Vulnerability
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 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 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.
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
This vulnerability is fixed in ConfD releases 7.4.3.1 and later and releases 7.5.2.1 and later.