Cisco Security Advisory
Cisco ASR 5000 Series Software Authorization Bypass Vulnerabilities
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CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H/E:X/RL:X/RC:X
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Multiple vulnerabilities in the authorization process of Cisco ASR 5000 Series Software (StarOS) could allow an authenticated, remote attacker to bypass authorization and execute a subset of CLI commands on an affected device.
For more information about these vulnerabilities, see the Details section of this advisory.
Cisco has released software updates that address these vulnerabilities. There are no workarounds that address these vulnerabilities.
This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asr5k-autho-bypass-mJDF5S7n
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Vulnerable Products
These vulnerabilities affect the following Cisco products if they are running a vulnerable release of Cisco StarOS:
- ASR 5000 Series Aggregation Services 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.
Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory are known to be affected by these vulnerabilities
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The vulnerabilities are not dependent on one another. Exploitation of one of the vulnerabilities is not required to exploit the other vulnerability. In addition, a software release that is affected by one of the vulnerabilities may not be affected by the other vulnerability.
Details about the vulnerabilities are as follows:
CVE-2021-1539: Cisco ASR 5000 Series Software TACACS Authorization Bypass Vulnerability
A vulnerability in the authorization process of Cisco ASR 5000 Series Software (StarOS) could allow an authenticated, remote attacker to bypass TACACS authorization on an affected device.
This vulnerability is due to incorrect authorization of non-interactive CLI commands. An attacker could exploit this vulnerability by sending a crafted Secure Shell (SSH) request to an affected device. A successful exploit could allow the attacker to bypass TACACS authorization and execute a subset of CLI commands on the affected device.
Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
Bug ID(s): CSCvu85001
CVE ID: CVE-2021-1539
Security Impact Rating (SIR): High
CVSS Base Score: 8.1
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:HCVE-2021-1540: Cisco ASR 5000 Series Software nocli Authorization Bypass Vulnerability
A vulnerability in the authorization process of Cisco ASR 5000 Series Software (StarOS) could allow an authenticated, remote attacker with an administrator account that is configured with the nocli option to bypass authorization on an affected device.
This vulnerability is due to incorrect authorization of non-interactive CLI commands. An attacker could exploit this vulnerability by sending a crafted SSH request to an affected device. A successful exploit could allow the attacker to bypass the nocli option and execute a subset of CLI commands on the affected device.
Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
Bug ID(s): CSCvv33622
CVE ID: CVE-2021-1540
Security Impact Rating (SIR): Medium
CVSS Base Score: 6.5
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:H
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There are no workarounds that address these vulnerabilities.
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Cisco has released free software updates that address the vulnerabilities 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.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.
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(s), the left column lists Cisco software releases. The right column indicates whether a release is affected by the vulnerabilities described in this advisory and the first release that includes the fix for these vulnerabilities. Customers are advised to upgrade to an appropriate fixed software release as indicated in this section.
Cisco StarOS Release First Fixed Release Earlier than 21.16 Migrate to 21.16.9 21.16 21.16.9 21.17 21.17.10 21.18 21.18.16 21.19 26.19.11 21.19.n 21.19.n7 21.20 21.20.8 21.21 and later Not vulnerable
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The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerabilities that are described in this advisory.
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These vulnerabilities were 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 1.0 Initial public release. - Final 2021-JUN-02
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