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AUSCERT External Security Bulletin Redistribution
ESB-2020.2924
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:
https://support.f5.com/csp/article/K11400411
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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)
Impact
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 - |12.1.5.2 | | | |
| | |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.
Mitigation
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:
empty_username_check
14. Select Branch Rules.
15. Select Add Branch Rule.
16. For Name, enter the following:
empty_username
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
procedure:
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
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