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             AUSCERT External Security Bulletin Redistribution

                  BIG-IP tmsh vulnerability CVE-2020-5858
                              8 October 2021


        AusCERT Security Bulletin Summary

Product:           BIG-IP modules
Publisher:         F5 Networks
Operating System:  Network Appliance
Impact/Access:     Execute Arbitrary Code/Commands -- Existing Account
Resolution:        Patch/Upgrade
CVE Names:         CVE-2020-5858  

Original Bulletin: 

Comment: The original publication date for this advisory was Mar 27, 2020. F5 updated the advisory on Oct 06, 2021.

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K36814487: BIG-IP tmsh vulnerability CVE-2020-5858

Original Publication Date: 27 Mar, 2020
Latest   Publication Date: 06 Oct, 2021

Security Advisory Description

Users with non-administrator roles (for example, Guest or Resource
Administrator) with TMOS Shell (tmsh) access can run arbitrary commands with
elevated privilege using a crafted tmsh command. (CVE-2020-5858)



This vulnerability allows unauthorized privileges to authenticated
non-administrator users who have tmsh access.

Traffix SDC

There is no impact; these F5 products are not affected by this vulnerability.

Security Advisory Status

F5 Product Development has assigned ID 818709 (BIG-IP), ID 826393 (BIG-IQ) 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|          |          |      |          |
|                   |15.x  |15.0.0 -  |15.1.0    |          |      |          |
|                   |      |15.0.1    |  |          |      |          |
|                   +------+----------+----------+          |      |          |
|BIG-IP (LTM, AAM,  |14.x  |14.0.0 -  |  |          |      |          |
|AFM, Analytics,    |      |14.1.2    |          |          |      |          |
|APM, ASM, DNS, Edge+------+----------+----------+          |      |          |
|Gateway, FPS, GTM, |13.x  |13.1.0 -  |  |High      |7.8   |tmsh      |
|Link Controller,   |      |13.1.3    |          |          |      |          |
|PEM,               +------+----------+----------+          |      |          |
|WebAccelerator)    |12.x  |12.1.0 -  |  |          |      |          |
|                   |      |12.1.5    |          |          |      |          |
|                   +------+----------+----------+          |      |          |
|                   |11.x  |11.5.2 -  |  |          |      |          |
|                   |      |11.6.5    |          |          |      |          |
|                   |8.x   |None      |8.0.0     |          |      |          |
|                   +------+----------+----------+          |      |          |
|                   |7.x   |7.0.0 -   |None      |          |      |          |
|                   |      |7.1.0     |          |          |      |          |
|BIG-IQ Centralized +------+----------+----------+High      |7.8   |tmsh      |
|Management         |6.x   |6.0.0 -   |None      |          |      |          |
|                   |      |6.1.0     |          |          |      |          |
|                   +------+----------+----------+          |      |          |
|                   |5.x   |5.2.0 -   |Will not  |          |      |          |
|                   |      |5.4.0     |fix       |          |      |          |
|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.


To mitigate this vulnerability, disable tmsh access for users with
non-administrator roles and grant administrative access only through the BIG-IP
Configuration utility.

To complete this mitigation, perform one of the following procedures:

Mitigating the vulnerability using the BIG-IP Configuration utility

 1. Log in to the BIG-IP Configuration utility as the admin user.
 2. Go to System > Users > User List.
 3. Select the Resource Administrator you want to modify.
 4. For Terminal Access select Disabled.
 5. Select Update.

Mitigating the vulnerability using tmsh

 1. Log in to tmsh as the root user.
 2. List the administrative users on your system.
 3. Use the following command syntax to disable tmsh for a user:

    modify /auth user <user> shell none

    Note: <user> is the name of the user for whom you want to disable tmsh 

    For example:

    modify /auth user test-user shell none

Supplemental Information

o K51812227: Understanding Security Advisory versioning
  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 - 15.x)
  o K15106: Managing BIG-IQ product hotfixes
  o K15113: BIG-IQ hotfix and point release matrix
  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
  o K21232150: Considerations for upgrading BIG-IQ or F5 iWorkflow systems

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