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AUSCERT External Security Bulletin Redistribution
ESB-2021.1903
Cisco ASR 5000 Series Software Authorization Bypass Vulnerabilities
3 June 2021
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AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco ASR 5000 Series Software
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Unauthorised Access -- Existing Account
Reduced Security -- Existing Account
Resolution: Patch/Upgrade
CVE Names: CVE-2021-1540 CVE-2021-1539
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asr5k-autho-bypass-mJDF5S7n
- --------------------------BEGIN INCLUDED TEXT--------------------
Cisco ASR 5000 Series Software Authorization Bypass Vulnerabilities
Priority: High
Advisory ID: cisco-sa-asr5k-autho-bypass-mJDF5S7n
First Published: 2021 June 2 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvu85001 CSCvv33622
CVE Names: CVE-2021-1539 CVE-2021-1540
CWEs: CWE-863
Summary
o 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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asr5k-autho-bypass-mJDF5S7n
Affected Products
o 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
Details
o 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:H
CVE-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
Workarounds
o There are no workarounds that address these vulnerabilities.
Fixed Software
o 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.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 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
Exploitation and Public Announcements
o 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.
Source
o These vulnerabilities were found during the resolution of a Cisco TAC
support case.
Cisco Security Vulnerability Policy
o 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.
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asr5k-autho-bypass-mJDF5S7n
Revision History
o +----------+---------------------------+----------+--------+--------------+
| Version | Description | Section | Status | Date |
+----------+---------------------------+----------+--------+--------------+
| 1.0 | Initial public release. | - | Final | 2021-JUN-02 |
+----------+---------------------------+----------+--------+--------------+
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