ESB-2018.3358 - [Appliance] F5 products: Overwrite arbitrary files - Existing account 2018-10-31

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             AUSCERT External Security Bulletin Redistribution

                               ESB-2018.3358
            K01067037: BIG-IP tmsh vulnerability CVE-2018-15321
                              31 October 2018

===========================================================================

        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           F5 products
Publisher:         F5 Networks
Operating System:  Network Appliance
Impact/Access:     Overwrite Arbitrary Files -- Existing Account
Resolution:        Patch/Upgrade
CVE Names:         CVE-2018-15321  

Original Bulletin: 
   https://support.f5.com/csp/article/K01067037

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K01067037: BIG-IP tmsh vulnerability CVE-2018-15321

Security Advisory

Original Publication Date: Oct 31, 2018

Security Advisory Description

When BIG-IP is licensed for Appliance mode, Admin and Resource administrator
roles can by-pass BIG-IP Appliance mode restrictions to overwrite critical
system files. (CVE-2018-15321)

Attackers with a high-privilege level can overwrite critical system files,
which in turn bypasses security controls that limit TMOS Shell (tmsh)
commands. This scenario is possible when the Administrator or Resource
Administrator roles are granted tmsh access. Resource Administrator roles must
have tmsh access to perform this attack.

Note:  F5 does not consider the capability of Advanced Shell (bash) access in
this vulnerability, as users granted that level of access can simply perform
any command as root.  This vulnerability is an issue for Appliance mode, users
who are granted tmsh access, and for the Resource Administrator role when
operating in standard, non-Appliance mode.

Impact

When the BIG-IP system is licensed for Appliance mode, Administrator and
Resource Administrator roles can by-pass BIG-IP Appliance mode restrictions to
overwrite critical system files.

Security Advisory Status

F5 Product Development has assigned ID 677088 (BIG-IP) and ID 705131 (BIG-IQ,
Enterprise Manager, and iWorkflow) 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 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|          |          |      |          |
+-------------------+------+----------+----------+----------+------+----------+
|                   |14.x  |14.0.0    |14.0.0.3  |          |      |          |
|                   +------+----------+----------+          |      |          |
|BIG-IP (LTM, AAM,  |13.x  |13.0.0 -  |13.1.0.6  |          |      |          |
|AFM, Analytics,    |      |13.1.0    |          |          |      |          |
|APM, ASM, DNS, Edge+------+----------+----------+          |      |TMSH      |
|Gateway, FPS, GTM, |12.x  |12.1.0 -  |12.1.3.6  |Medium    |4.4   |advanced  |
|Link Controller,   |      |12.1.3    |          |          |      |shell     |
|PEM,               +------+----------+----------+          |      |          |
|WebAccelerator)    |      |11.6.0 -  |          |          |      |          |
|                   |11.x  |11.6.3    |11.6.3.3  |          |      |          |
|                   |      |11.2.1 -  |11.5.7    |          |      |          |
|                   |      |11.5.6    |          |          |      |          |
+-------------------+------+----------+----------+----------+------+----------+
|                   |      |          |          |          |      |TMSH      |
|Enterprise Manager |3.x   |3.1.1     |None      |Medium    |4.4   |advanced  |
|                   |      |          |          |          |      |shell     |
+-------------------+------+----------+----------+----------+------+----------+
|                   |6.x   |None      |Not       |          |      |          |
|                   |      |          |applicable|          |      |          |
|BIG-IQ Centralized +------+----------+----------+          |      |TMSH      |
|Management         |5.x   |5.0.0 -   |None      |Medium    |4.4   |advanced  |
|                   |      |5.4.0     |          |          |      |shell     |
|                   +------+----------+----------+          |      |          |
|                   |4.x   |4.6.0     |None      |          |      |          |
+-------------------+------+----------+----------+----------+------+----------+
|BIG-IQ Cloud and   |      |          |          |          |      |TMSH      |
|Orchestration      |1.x   |1.0.0     |None      |Medium    |4.4   |advanced  |
|                   |      |          |          |          |      |shell     |
+-------------------+------+----------+----------+----------+------+----------+
|                   |      |2.1.0 -   |          |          |      |TMSH      |
|F5 iWorkflow       |2.x   |2.3.0     |None      |Medium    |4.4   |advanced  |
|                   |      |          |          |          |      |shell     |
+-------------------+------+----------+----------+----------+------+----------+
|                   |5.x   |None      |Not       |          |      |          |
|                   |      |          |applicable|Not       |      |          |
|Traffix SDC        +------+----------+----------+vulnerable|None  |None      |
|                   |4.x   |None      |Not       |          |      |          |
|                   |      |          |applicable|          |      |          |
+-------------------+------+----------+----------+----------+------+----------+

^1 The 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, disable tmsh access for users with the Resource
Administrator role, and grant administration access only by way of the BIG-IP
Configuration utility.

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

Mitigate the vulnerability using the BIG-IP Configuration utility

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

Mitigate 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.
    (Where <user> is the name of the user for whom you would like to disable
    tmsh.)

    modify /auth user <user> shell none

    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 - 13.x)
  o K15106: Managing BIG-IQ product hotfixes
  o K15113: BIG-IQ hotfix 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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