ESB-2018.1012 - [Appliance] F5 BIG-IP Products: Root compromise - Existing account 2018-04-05

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===========================================================================
             AUSCERT External Security Bulletin Redistribution

                               ESB-2018.1012
            K18015201:Linux kernel vulnerability CVE-2017-2636
                               5 April 2018

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

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

Product:           F5 BIG-IP Products
Publisher:         F5 Networks
Operating System:  Network Appliance
Impact/Access:     Root Compromise -- Existing Account
Resolution:        Patch/Upgrade
CVE Names:         CVE-2017-2636  

Reference:         ESB-2017.3225.2
                   ESB-2017.2214
                   ESB-2017.1521
                   ESB-2017.1031
                   ESB-2017.0950

Original Bulletin: 
   https://support.f5.com/csp/article/K18015201

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K18015201:Linux kernel vulnerability CVE-2017-2636

Security Advisory

Original Publication Date: 29 Mar, 2017

Latest   Publication Date: 04 Apr, 2018

Security Advisory Description

Race condition in drivers/tty/n_hdlc.c in the Linux kernel through 4.10.1
allows local users to gain privileges or cause a denial of service (double
free) by setting the HDLC line discipline. (CVE-2017-2636)

Impact

This vulnerability may allow locally authenticated users to cause a denial of
service (DoS) or gain privileges with unauthorized access to view information
or make modifications. This vulnerability is considered local, as it is
exploitable only by an authenticated user accessing the system using the
command line. Additionally, the n_hdlc kernel module must be loaded in order
for F5 products to be vulnerable to this issue. F5 products do not load the
n_hdlc kernel module by default.

Note: Chained exploitation is required for privilege escalation.


Security Advisory Status

F5 Product Development has assigned IDs 651243 and 651245 (BIG-IP), ID 651300
(BIG-IQ, iWorkflow), and ID 651295 (Enterprise Manager) to this vulnerability.
Additionally, BIG-IP iHealth may list Heuristic H18015201 on the Diagnostics >
Identified > Medium screen.

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:

+---------------+---------------+-----------------+----------+---------------+
|               |Versions known |Versions known to|          |Vulnerable     |
|Product        |to be          |be not vulnerable|Severity  |component or   |
|               |vulnerable     |                 |          |feature        |
+---------------+---------------+-----------------+----------+---------------+
|               |               |13.0.1           |          |               |
|BIG-IP LTM     |13.0.0         |12.0.0 - 12.1.2  |Medium    |Linux kernel   |
|               |               |11.4.0 - 11.6.1  |          |               |
|               |               |11.2.1           |          |               |
+---------------+---------------+-----------------+----------+---------------+
|               |13.0.0         |13.0.1           |          |               |
|BIG-IP AAM     |               |12.0.0 - 12.1.2  |Medium    |Linux kernel   |
|               |               |11.4.0 - 11.6.1  |          |               |
+---------------+---------------+-----------------+----------+---------------+
|               |13.0.0         |13.0.1           |          |               |
|BIG-IP AFM     |               |12.0.0 - 12.1.2  |Medium    |Linux kernel   |
|               |               |11.4.0 - 11.6.1  |          |               |
+---------------+---------------+-----------------+----------+---------------+
|               |               |13.0.1           |          |               |
|BIG-IP         |13.0.0         |12.0.0 - 12.1.2  |Medium    |Linux kernel   |
|Analytics      |               |11.4.0 - 11.6.1  |          |               |
|               |               |11.2.1           |          |               |
+---------------+---------------+-----------------+----------+---------------+
|               |               |13.0.1           |          |               |
|BIG-IP APM     |13.0.0         |12.0.0 - 12.1.2  |Medium    |Linux kernel   |
|               |               |11.4.0 - 11.6.1  |          |               |
|               |               |11.2.1           |          |               |
+---------------+---------------+-----------------+----------+---------------+
|               |               |13.0.1           |          |               |
|BIG-IP ASM     |13.0.0         |12.0.0 - 12.1.2  |Medium    |Linux kernel   |
|               |               |11.4.0 - 11.6.1  |          |               |
|               |               |11.2.1           |          |               |
+---------------+---------------+-----------------+----------+---------------+
|BIG-IP DNS     |13.0.0         |13.0.1           |Medium    |Linux kernel   |
|               |               |12.0.0 - 12.1.2  |          |               |
+---------------+---------------+-----------------+----------+---------------+
|BIG-IP Edge    |None           |11.2.1           |Medium    |Linux kernel   |
|Gateway        |               |                 |          |               |
+---------------+---------------+-----------------+----------+---------------+
|BIG-IP GTM     |None           |11.4.0 - 11.6.1  |Medium    |Linux kernel   |
|               |               |11.2.1           |          |               |
+---------------+---------------+-----------------+----------+---------------+
|               |               |13.0.1           |          |               |
|BIG-IP Link    |13.0.0         |12.0.0 - 12.1.2  |Medium    |Linux kernel   |
|Controller     |               |11.4.0 - 11.6.1  |          |               |
|               |               |11.2.1           |          |               |
+---------------+---------------+-----------------+----------+---------------+
|               |               |13.0.1           |          |               |
|BIG-IP PEM     |13.0.0         |12.0.0 - 12.1.2  |Medium    |Linux kernel   |
|               |               |11.4.0 - 11.6.1  |          |               |
+---------------+---------------+-----------------+----------+---------------+
|BIG-IP PSM     |None           |11.4.0 - 11.4.1  |Medium    |Linux kernel   |
+---------------+---------------+-----------------+----------+---------------+
|BIG-IP         |None           |11.2.1           |Medium    |Linux kernel   |
|WebAccelerator |               |                 |          |               |
+---------------+---------------+-----------------+----------+---------------+
|               |               |13.0.1           |          |               |
|BIG-IP WebSafe |13.0.0         |12.0.0 - 12.1.2  |Medium    |Linux kernel   |
|               |               |11.6.0 - 11.6.1  |          |               |
+---------------+---------------+-----------------+----------+---------------+
|ARX            |None           |6.2.0 - 6.4.0    |Not       |None           |
|               |               |                 |vulnerable|               |
+---------------+---------------+-----------------+----------+---------------+
|Enterprise     |3.1.1          |None             |Medium    |Linux kernel   |
|Manager        |               |                 |          |               |
+---------------+---------------+-----------------+----------+---------------+
|BIG-IQ Cloud   |4.0.0 - 4.5.0  |None             |Medium    |Linux kernel   |
+---------------+---------------+-----------------+----------+---------------+
|BIG-IQ Device  |4.2.0 - 4.5.0  |None             |Medium    |Linux kernel   |
+---------------+---------------+-----------------+----------+---------------+
|BIG-IQ Security|4.0.0 - 4.5.0  |None             |Medium    |Linux kernel   |
+---------------+---------------+-----------------+----------+---------------+
|BIG-IQ ADC     |4.5.0          |None             |Medium    |Linux kernel   |
+---------------+---------------+-----------------+----------+---------------+
|BIG-IQ         |5.0.0 - 5.1.0  |                 |          |               |
|Centralized    |4.6.0          |None             |Medium    |Linux kernel   |
|Management     |               |                 |          |               |
+---------------+---------------+-----------------+----------+---------------+
|BIG-IQ Cloud   |               |                 |          |               |
|and            |1.0.0          |None             |Medium    |Linux kernel   |
|Orchestration  |               |                 |          |               |
+---------------+---------------+-----------------+----------+---------------+
|F5 iWorkflow   |2.0.0 - 2.1.0  |None             |Medium    |Linux kernel   |
+---------------+---------------+-----------------+----------+---------------+
|LineRate       |None           |2.5.0 - 2.6.2    |Not       |None           |
|               |               |                 |vulnerable|               |
+---------------+---------------+-----------------+----------+---------------+
|Traffix SDC    |5.0.0 - 5.1.0  |None             |Low       |Linux kernel   |
|               |4.0.0 - 4.4.0  |                 |          |               |
+---------------+---------------+-----------------+----------+---------------+

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 Versions known to be not vulnerable 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 determine the necessary upgrade path for your BIG-IQ system, you should
understand the BIG-IQ product offering name changes. For more information,
refer to K21232150: Considerations for upgrading BIG-IQ or F5 iWorkflow
systems.

Mitigation

To confirm the status of the n_hdlc kernel module, you can use the lsmod |
grep -i n_hdlc Linux command from the command line of the F5 product. If the
n_hdlc module is loaded, output appears similar to the following example:

# lsmod | grep -i n_hdlc
n_hdlc                 17455  0

To mitigate this vulnerability, you can blacklist the n_hdlc module to prevent
accidental or intentional loading. To do so, perform the following procedure:

Impact of action: Performing the following procedure should not have a
negative impact on your system.

 1. Log in to the command line of the F5 product as the root user.
 2. To prevent accidental or intentional loading of the n_hdlc module, type
    the following command:

    echo "install n_hdlc /bin/true" >> /etc/modprobe.d/disable-n_hdlc.conf

 3. Optional: If the n_hdlc module is already loaded and in use by a process,
    then reboot the system.

You can also mitigate this vulnerability by permitting management access to
the F5 product only over a secure network and limiting shell access to trusted
users. For more information, refer to K5380: Specifying allowable IP ranges
for SSH access and K13092: Overview of securing access to the BIG-IP system.


Supplemental Information

  o K9970: Subscribing to email notifications regarding F5 products
  o K9957: Creating a custom RSS feed to view new and updated documents
  o K4602: Overview of the F5 security vulnerability response policy
  o K4918: Overview of the F5 critical issue hotfix policy
  o K167: Downloading software and firmware from F5

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