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             AUSCERT External Security Bulletin Redistribution

                               ESB-2021.1448
  Appliance Mode authenticated iControl REST vulnerability CVE-2021-23015
                               29 April 2021

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

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

Product:           BIG-IP products
Publisher:         F5 Networks
Operating System:  Network Appliance
Impact/Access:     Execute Arbitrary Code/Commands -- Existing Account
Resolution:        Patch/Upgrade
CVE Names:         CVE-2021-23015  

Reference:         ESB-2021.0879
                   ESB-2021.0870.2

Original Bulletin: 
   https://support.f5.com/csp/article/K74151369

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K74151369: Appliance Mode authenticated iControl REST vulnerability
CVE-2021-23015

Original Publication Date: 29 Apr, 2021

Security Advisory Description

When running in Appliance Mode, an authenticated user assigned the
'Administrator' role may be able to bypass Appliance Mode restrictions
utilizing undisclosed iControl REST endpoints. (CVE-2021-23015)

Note: This vulnerability is unrelated to the vulnerability described in the
following article: K03009991: iControl REST unauthenticated remote command
execution vulnerability CVE-2021-22986.

Impact

In Appliance Mode, an authenticated user with valid user credentials assigned
the Administrator role may be able to bypass appliance mode restrictions and
run arbitrary commands. This is a control plane issue; there is no data plane
exposure. Appliance Mode is enforced by a specific license or may be enabled or
disabled for individual Virtual Clustered Multiprocessing (vCMP) guest
instances. For information on Appliance mode, refer to: K12815: Overview of
Appliance mode. 

Note: If you believe your system may have been compromised, refer to K11438344:
Considerations and guidance when you suspect a security compromise on a BIG-IP
system.

Security Advisory Status

F5 Product Development has assigned ID 959121, ID 1003105, and ID 1003557
(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.

Note: After a fix is introduced for a given minor branch, that fix applies to
all subsequent maintenance and point releases for that branch, and no
additional fixes for that branch will be listed in the table. For example, when
a fix is introduced in 14.1.2.3, the fix also applies to 14.1.2.4, and all
later 14.1.x releases (14.1.3.x., 14.1.4.x). For more information, refer to
K51812227: Understanding security advisory versioning. Additionally, software
versions preceding those listed in the following table have reached the End of
Technical Support (EoTS) phase of their lifecycle and are no longer evaluated
for security issues. For more information, refer to the Security hotfixes
section of K4602: Overview of the F5 security vulnerability response policy.

+------------+------+-------------+----------+-----------+------+-------------+
|            |      |Versions     |Fixes     |           |CVSSv3|Vulnerable   |
|Product     |Branch|known to be  |introduced|Severity   |score^|component or |
|            |      |vulnerable^1 |in        |           |2     |feature      |
+------------+------+-------------+----------+-----------+------+-------------+
|            |16.x  |16.0.0 -     |None      |           |      |             |
|            |      |16.0.1       |          |           |      |             |
|            +------+-------------+----------+           |      |             |
|            |15.x  |15.1.0 -     |15.1.3    |           |      |             |
|            |      |15.1.2       |          |           |      |             |
|            +------+-------------+----------+           |      |             |
|            |14.x  |14.1.0 -     |14.1.4.2  |High -     |      |             |
|BIG-IP (all |      |14.1.4       |          |Appliance  |      |             |
|modules)    +------+-------------+----------+Mode Only^3|8.7   |iControl REST|
|            |13.x  |13.1.0.8 -   |13.1.4    |           |      |             |
|            |      |13.1.3       |          |           |      |             |
|            +------+-------------+----------+           |      |             |
|            |12.x  |None         |Not       |           |      |             |
|            |      |             |applicable|           |      |             |
|            +------+-------------+----------+           |      |             |
|            |11.x  |None         |Not       |           |      |             |
|            |      |             |applicable|           |      |             |
+------------+------+-------------+----------+-----------+------+-------------+
|            |8.x   |None         |Not       |           |      |             |
|            |      |             |applicable|           |      |             |
|BIG-IQ      +------+-------------+----------+           |      |             |
|Centralized |7.x   |None         |Not       |Not        |None  |None         |
|Management  |      |             |applicable|vulnerable |      |             |
|            +------+-------------+----------+           |      |             |
|            |6.x   |None         |Not       |           |      |             |
|            |      |             |applicable|           |      |             |
+------------+------+-------------+----------+-----------+------+-------------+
|F5OS        |1.x   |None         |Not       |Not        |None  |None         |
|            |      |             |applicable|vulnerable |      |             |
+------------+------+-------------+----------+-----------+------+-------------+
|Traffix SDC |5.x   |None         |Not       |Not        |None  |None         |
|            |      |             |applicable|vulnerable |      |             |
+------------+------+-------------+----------+-----------+------+-------------+

^1F5 evaluates only software versions that have not yet reached the End of
Technical Support (EoTS) phase of their lifecycle.

^2The CVSSv3 score link takes you to a resource outside of AskF5, and it is
possible that the document may be removed without our knowledge.

^3This vulnerability exists for only the limited number of customers using
Appliance Mode. For information on Appliance mode, refer to: K12815: Overview
of Appliance mode.

Recommended Actions

If you are running a version listed in the Versions known to be vulnerable
column, you can eliminate this vulnerability by installing a version listed in
the Fixes introduced in column. If the Fixes introduced in column does not list
a version for your branch, then no update candidate currently exists for that
branch and F5 recommends upgrading to a version with the fix (refer to the
table).

If the Fixes introduced in column lists a version prior to the one you are
running, in the same branch, then your version should have the fix.

Mitigation

F5 suggests that you audit users assigned the Administrator role in any
installations and limit the number of users assigned that role. As the
vulnerability is exposed only to users assigned the Administrator role,
consider reducing privileges, where possible, to Resource Administrator or
lower.

Until you can install a fixed version, you can use the following sections as
temporary mitigations. These mitigations restrict access to iControl REST to
only trusted networks or devices, thereby limiting the attack surface. Note
that the attack must be carried out by an attacker who holds valid credentials
to a highly privileged administrative account. Therefore, restricting access
may still leave the device exposed to the risk of a malicious insider or
lateral movement from another compromised device within the trusted range.

  o Block iControl REST access through the self IP address
  o Block iControl REST access through the management interface

Block iControl REST access through the self IP address

You can block all access to the iControl REST interface of your BIG-IP system
through self IP addresses. To do so, you can change the Port Lockdown setting
to Allow None for each self IP address in the system. If you must open any
ports, you should use the Allow Custom option, taking care to disallow access
to iControl REST. By default, iControl REST listens on TCP port 443.
Alternatively, you can configure a custom port.

Note: Performing this action prevents all access to the Configuration utility
and iControl REST using the self IP address. These changes may also impact
other services, including breaking high availability (HA) configurations.

Before you make changes to the configuration of your self-IP addresses, F5
strongly recommends that you refer to the following articles:

  o K17333: Overview of port lockdown behavior (12.x - 16.x)
  o K13092: Overview of securing access to the BIG-IP system
  o K31003634: The Configuration utility of the Single-NIC BIG-IP Virtual
    Edition now defaults to TCP port 8443
  o K51358480: The single-NIC BIG-IP VE may erroneously revert to the default
    management httpd port after a configuration reload

If you must expose port 443 on your self IP addresses and want to restrict
access to specific IP ranges, you may consider using the packet filtering
functionality built in to the BIG-IP system. For more information, refer to the
following article:

  o K13383: Configuring CIDR Network Addresses for the BIG-IP packet filter

Block iControl REST access through the management interface

To mitigate this vulnerability for affected F5 products, you should restrict
management access to only trusted users and devices over a secure network. For
more information about securing access to BIG-IP systems, refer to the
following articles:

  o K13092: Overview of securing access to the BIG-IP system
  o K46122561: Restricting access to the management interface using network
    firewall rules 
  o K69354049: Restricting access to the BIG-IP management interface for
    Configuration Utility and iControl REST services using iptables

Note: Restricting access to the management interface by IP address in httpd is
not a viable mitigation for this issue.

Acknowledgements

F5 acknowledges the following Security Researchers for bringing this issue to
our attention and following the highest standards of coordinated disclosure:

  o William Vu of Rapid7
  o HTTPVoid (Rahul Maini & Harsh Jaiswal)
  o The Unisys Security Incident Response Team

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 K15106: Managing BIG-IQ product hotfixes
  o K15113: BIG-IQ hotfix and point release matrix
  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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