Hash: SHA256

             AUSCERT External Security Bulletin Redistribution

       BIG-IP APM RADIUS authentication vulnerability CVE-2020-5924
                              26 August 2020


        AusCERT Security Bulletin Summary

Product:           BIG-IP APM
Publisher:         F5 Networks
Operating System:  Network Appliance
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2020-5924  

Original Bulletin: 

- --------------------------BEGIN INCLUDED TEXT--------------------

K11400411:BIG-IP APM RADIUS authentication vulnerability CVE-2020-5924

Security Advisory

Original Publication Date: 26 Aug, 2020

Security Advisory Description

RADIUS authentication leaks memory when the username for authentication is not
set. (CVE-2020-5924)


This issue may lead to excessive memory consumption. On a BIG-IP system that is
configured for high availability (HA), this vulnerability may cause a failover
event and temporarily disrupt services.

Security Advisory Status

F5 Product Development has assigned ID 883097 (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 or  |
|               |      |be        |in        |          |1     |feature       |
|               |      |vulnerable|          |          |      |              |
|               |16.x  |None      |Not       |          |      |              |
|               |      |          |applicable|          |      |              |
|               +------+----------+----------+          |      |              |
|               |15.x  |None      |Not       |          |      |              |
|               |      |          |applicable|          |      |              |
|               +------+----------+----------+          |      |              |
|               |14.x  |None      |Not       |          |      |BIG-IP APM    |
|BIG-IP (APM)   |      |          |applicable|Medium    |5.3   |radius        |
|               +------+----------+----------+          |      |authentication|
|               |13.x  |None      |13.0.0    |          |      |              |
|               +------+----------+----------+          |      |              |
|               |12.x  |12.1.0 -  |  |          |      |              |
|               |      |12.1.5    |          |          |      |              |
|               +------+----------+----------+          |      |              |
|               |11.x  |11.6.1 -  |None      |          |      |              |
|               |      |11.6.5    |          |          |      |              |
|               |15.x  |None      |Not       |          |      |              |
|               |      |          |applicable|          |      |              |
|               +------+----------+----------+          |      |              |
|BIG-IP (LTM,   |14.x  |None      |Not       |          |      |              |
|AAM, AFM,      |      |          |applicable|          |      |              |
|Analytics, ASM,+------+----------+----------+          |      |              |
|DNS, FPS, GTM, |13.x  |None      |Not       |Not       |None  |None          |
|Link           |      |          |applicable|vulnerable|      |              |
|Controller,    +------+----------+----------+          |      |              |
|PEM)           |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.

Security Advisory 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.


To mitigate this vulnerability, in the Visual Policy Editor (VPE) of the access
policy, you can create an action between the logon page and the Radius Auth
agent to ensure that the username is not empty before allowing the user logon
to proceed to the Radius Auth agent. To do so, you can create an Empty action
with a branch rule using the following expression:

expr {[mcget {session.logon.last.username}] == ""}

To allow users three attempts, you should create this action in a macro. To do
so, perform the following procedure:

Impact of action: Performing the following procedure should not have a negative
impact on your system. However, as authentication differs between different
environments, F5 recommends that you test the changes in a staging environment
first before implementing in production.

 1. Log in to the Configuration utility.
 2. Go to Access > Profiles /Policies.

    Note: For versions prior to 13.x, go to Access Policy > Access Profiles.

 3. Next to the name of the affected Access Profile, select Edit.
 4. Create a new macro to verify that the username is not empty by performing
    the following procedure. This macro contains a logon page and an action to
    verify that the username is not empty, allowing the user three attempts.
     1. Select Add New Macro.
     2. For Name, enter Empty_username_check_macro.
     3. Select Save.
     4. To expand the new macro, select the +.
     5. Select Macro Settings / Rename.
     6. For Maximum Macro Loop Count, select 3.
     7. Select Save.
     8. To create a logon page, select the +.
     9. Select Logon Page and Add Item.
    10. Make any required customizations and select Save.
    11. Select the + after Logon Page.
    12. Under the General Purpose tab, select Empty and Add Item.
    13. For Name, enter the following:


    14. Select Branch Rules.
    15. Select Add Branch Rule.
    16. For Name, enter the following:


    17. Select change.
    18. Select Advanced.
    19. Paste the following content into the text field.

        expr {[mcget {session.logon.last.username}] == ""}

    20. Select Finished.
    21. Select Save.
    22. Select Out next to the empty_username branch.
    23. Select Loop and Save.
 5. Once you create the macro, replace the existing logon page with the new
    macro for the actions to take effect, by performing the following
     1. To add the new macro, select the + between the Logon Page and Radius
        Auth agent.
     2. Select the Macros tab.
     3. Select the newly created macro and select Add Item.
     4. To remove the original logon page, select the X associated with the
        Logon Page.
     5. Select Delete.
 6. To apply the changes, click Apply Access Policy.

Supplemental Information

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--------------------

You have received this e-mail bulletin as a result of your organisation's
registration with AusCERT. The mailing list you are subscribed to is
maintained within your organisation, so if you do not wish to continue
receiving these bulletins you should contact your local IT manager. If
you do not know who that is, please send an email to auscert@auscert.org.au
and we will forward your request to the appropriate person.

NOTE: Third Party Rights
This security bulletin is provided as a service to AusCERT's members.  As
AusCERT did not write the document quoted above, AusCERT has had no control
over its content. The decision to follow or act on information or advice
contained in this security bulletin is the responsibility of each user or
organisation, and should be considered in accordance with your organisation's
site policies and procedures. AusCERT takes no responsibility for consequences
which may arise from following or acting on information or advice contained in
this security bulletin.

NOTE: This is only the original release of the security bulletin.  It may
not be updated when updates to the original are made.  If downloading at
a later date, it is recommended that the bulletin is retrieved directly
from the author's website to ensure that the information is still current.

Contact information for the authors of the original document is included
in the Security Bulletin above.  If you have any questions or need further
information, please contact them directly.

Previous advisories and external security bulletins can be retrieved from:


Australian Computer Emergency Response Team
The University of Queensland
Qld 4072

Internet Email: auscert@auscert.org.au
Facsimile:      (07) 3365 7031
Telephone:      (07) 3365 4417 (International: +61 7 3365 4417)
                AusCERT personnel answer during Queensland business hours
                which are GMT+10:00 (AEST).
                On call after hours for member emergencies only.
Comment: http://www.auscert.org.au/render.html?it=1967