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AUSCERT External Security Bulletin Redistribution
ESB-2021.1450
BIG-IP APM AD authentication vulnerability CVE-2021-23008
29 April 2021
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: BIG-IP APM
Publisher: F5 Networks
Operating System: Network Appliance
Impact/Access: Administrator Compromise -- Remote/Unauthenticated
Provide Misleading Information -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2021-23008
Original Bulletin:
https://support.f5.com/csp/article/K51213246
- --------------------------BEGIN INCLUDED TEXT--------------------
K51213246: BIG-IP APM AD authentication vulnerability CVE-2021-23008
Original Publication Date: 29 Apr, 2021
Security Advisory Description
BIG-IP APM AD (Active Directory) authentication can be bypassed using a spoofed
AS-REP (Kerberos Authentication Service Response) response sent over a hijacked
KDC (Kerberos Key Distribution Center) connection, or from an AD server
compromised by an attacker.(CVE-2021-23008)
Impact
A remote attacker can hijack a KDC connection using a spoofed AS-REP response.
For an APM access policy configured with AD authentication and SSO (single
sign-on) agent, if a spoofed credential related to this vulnerability is used,
depending how the back-end system validates the authentication token it
receives, access will most likely fail. An APM access policy can also be
configured for BIG-IP system authentication. A spoofed credential related to
this vulnerability for an administrative user through the APM access policy
results in local administrative access.
Security Advisory Status
F5 Product Development has assigned ID 882633 (BIG-IP) to this vulnerability.
To determine if your product and version have been evaluated for this
vulnerability, refer to the Applies to (see versions) box. To determine if your
release is known to be vulnerable, the components or features that are affected
by the vulnerability, and for information about releases, point releases, or
hotfixes that address the vulnerability, refer to the following table. For more
information about security advisory versioning, refer to K51812227:
Understanding Security Advisory versioning.
+-------------------+------+----------+----------+----------+------+----------+
| | |Versions |Fixes | |CVSSv3|Vulnerable|
|Product |Branch|known to |introduced|Severity |score^|component |
| | |be |in | |1 |or feature|
| | |vulnerable| | | | |
+-------------------+------+----------+----------+----------+------+----------+
| |16.x |16.0.0 - |None | | | |
| | |16.0.1 | | | | |
| +------+----------+----------+ | | |
| |15.x |15.0.0 - |15.1.3 | | | |
| | |15.1.2 | | | | |
| +------+----------+----------+ | | |
| |14.x |14.1.0 - |14.1.4 | | | |
| | |14.1.3 | | | |APM AD |
|BIG-IP APM +------+----------+----------+High |8.1 |auth |
| |13.x |13.1.0 - |13.1.4 | | | |
| | |13.1.3 | | | | |
| +------+----------+----------+ | | |
| |12.x |12.1.0 - |12.1.6 | | | |
| | |12.1.5 | | | | |
| +------+----------+----------+ | | |
| |11.x |11.5.2 - |None | | | |
| | |11.6.5 | | | | |
+-------------------+------+----------+----------+----------+------+----------+
| |16.x |None |Not | | | |
| | | |applicable| | | |
| +------+----------+----------+ | | |
| |15.x |None |Not | | | |
| | | |applicable| | | |
| +------+----------+----------+ | | |
|BIG-IP (LTM, AAM, |14.x |None |Not | | | |
|AFM, Analytics, | | |applicable|Not | | |
|ASM, DNS, FPS, GTM,+------+----------+----------+vulnerable|None |None |
|Link Controller, |13.x |None |Not | | | |
|PEM) | | |applicable| | | |
| +------+----------+----------+ | | |
| |12.x |None |Not | | | |
| | | |applicable| | | |
| +------+----------+----------+ | | |
| |11.x |None |Not | | | |
| | | |applicable| | | |
+-------------------+------+----------+----------+----------+------+----------+
| |7.x |None |Not | | | |
| | | |applicable| | | |
| +------+----------+----------+ | | |
|BIG-IQ Centralized |6.x |None |Not |Not |None |None |
|Management | | |applicable|vulnerable| | |
| +------+----------+----------+ | | |
| |5.x |None |Not | | | |
| | | |applicable| | | |
+-------------------+------+----------+----------+----------+------+----------+
|Traffix SDC |5.x |None |Not |Not |None |None |
| | | |applicable|vulnerable| | |
+-------------------+------+----------+----------+----------+------+----------+
^1The CVSSv3 score link takes you to a resource outside of AskF5, and it is
possible that the document may be removed without our knowledge.
Recommended Actions
If you are running a version listed in the Versions known to be vulnerable
column, you can eliminate this vulnerability by upgrading to a version listed
in the Fixes introduced in column. If the table lists only an older version
than what you are currently running, or does not list a non-vulnerable version,
then no upgrade candidate currently exists.
Mitigation
APM access policy
To mitigate this vulnerability, you can configure multi-factor authentication
(MFA), or host-level authentication, such as deploying an IPSec tunnel between
the affected BIG-IP APM system and the AD servers.
BIG-IP System authentication
If BIG-IP system authentication uses AD authentication from an APM access
policy, you can use an alternative remote authentication option from the User
Directory options that have the SSL-based authentication feature. The key
configuration enables the 'SSL' option and configures it as needed for the
listed remote authentication alternative configurations:
o Active Directory
o LDAP
o ClientCert LDAP
Impact: Performing the recommended procedures should not have a negative impact
on your system.
Note: For more information, refer to the Configuring IPsec between a BIG-IP
System and a Third-Party Device chapter of the BIG-IP TMOS: Tunneling and
IPsec guide and the Configuring Remote User Authentication and Authorization
chapter in the BIG-IP TMOS: Implementations guide.
Note: For information about how to locate F5 product manuals, refer to
K98133564: Tips for searching AskF5 and finding product documentation.
Acknowledgements
F5 would like to acknowledge Yaron Kassner and Rotem Zach from Silverfort and
Thierry Van Steirteghem from Exclusive Networks for bringing this issue to our
attention and for following the highest standards of coordinated disclosure.
Supplemental Information
o The Kerberos Network Authentication Service (V5) RFC4120
o K42422282: Configuring Multi-factor Authentication
o K79345554: Reasons why an established IPsec tunnel fails to forward packets
o K41942608: Overview of Security Advisory articles
o K4602: Overview of the F5 security vulnerability response policy
o K4918: Overview of the F5 critical issue hotfix policy
o K9502: BIG-IP hotfix and point release matrix
o K13123: Managing BIG-IP product hotfixes (11.x - 16.x)
o K48955220: Installing an OPSWAT Endpoint Security update on BIG-IP APM
systems (11.4.x and later)
o K167: Downloading software and firmware from F5
o K9970: Subscribing to email notifications regarding F5 products
o K9957: Creating a custom RSS feed to view new and updated documents
- --------------------------END INCLUDED TEXT--------------------
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