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             AUSCERT External Security Bulletin Redistribution

                     NTP vulnerability CVE-2020-11868
                                3 June 2020


        AusCERT Security Bulletin Summary

Product:           BIG-IP products
                   BIG-IQ Centralized Management
                   Traffix SDC
Publisher:         F5 Networks
Operating System:  Network Appliance
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Mitigation
CVE Names:         CVE-2020-11868  

Reference:         ESB-2020.1596

Original Bulletin: 

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K44305703:NTP vulnerability CVE-2020-11868

Security Advisory

Original Publication Date: 03 Jun, 2020

Security Advisory Description

The ntpd daemon in ntp before 4.2.8p14 and 4.3.x before 4.3.100 allows an
off-path attacker to block unauthenticated synchronization via a server mode
packet with a spoofed source IP address, because transmissions are rescheduled
even when a packet lacks a valid origin timestamp. (CVE-2020-11868)


Attackers who can guess the IP address of configured time server(s) and deliver
a spoofed packet to TMOS systems may delay communication with time servers,
potentially causing a loss of clock synchronization.

Security Advisory Status

F5 Product Development has assigned ID 912797 (BIG-IP), ID 912829 (BIG-IQ) and
CPF-25198, CPF-25199 (Traffix) 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 -  |None      |        |      |          |
|                     |      |15.1.0    |          |        |      |          |
|                     +------+----------+----------+        |      |          |
|                     |14.x  |14.1.0 -  |None      |        |      |          |
|                     |      |14.1.2    |          |        |      |          |
|BIG-IP (LTM, AAM,    +------+----------+----------+        |      |          |
|AFM, Analytics, APM, |13.x  |13.1.0 -  |None      |Low     |3.7   |NTP       |
|ASM, DNS, FPS, GTM,  |      |13.1.3    |          |        |      |          |
|Link Controller, PEM)+------+----------+----------+        |      |          |
|                     |12.x  |12.1.0 -  |None      |        |      |          |
|                     |      |12.1.5    |          |        |      |          |
|                     +------+----------+----------+        |      |          |
|                     |11.x  |11.6.1 -  |None      |        |      |          |
|                     |      |11.6.5    |          |        |      |          |
|                     |7.x   |7.0.0 -   |None      |        |      |          |
|                     |      |7.1.0     |          |        |      |          |
|                     +------+----------+----------+        |      |          |
|BIG-IQ Centralized   |6.x   |6.0.0 -   |None      |Low     |3.7   |NTP       |
|Management           |      |6.1.0     |          |        |      |          |
|                     +------+----------+----------+        |      |          |
|                     |5.x   |5.2.0 -   |None      |        |      |          |
|                     |      |5.4.0     |          |        |      |          |
|Traffix SDC          |5.x   |5.1.0     |None      |Low     |3.7   |NTP       |

^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.


To mitigate this vulnerability, you can perform one of the following
recommended modifications to the NTP service:

  o Configuring authentication with symmetric keys for complete mitigation.
  o Configuring the NTP service to use multiple time sources to reduce the risk
    of the vulnerability.

Configuring authentication with symmetric keys

For complete mitigation, configure authentication on the time sources. For the
BIG-IP system, refer to the Symmetric key authentication section in K14120:
Defining advanced NTP configurations on the BIG-IP system (11.x - 15.x).

Configuring the NTP service to use multiple time sources

To reduce the risk of the vulnerability, you can add multiple time sources for
the NTP service. For the BIG-IP system, 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 Configuration utility.
 2. Navigate to System > Configuration > Device > NTP.
 3. In the Address box, enter the IP address of the NTP server you want.
 4. In the Time Server List box, include the desired NTP server by selecting
 5. Repeat step 3 and step 4 for each NTP server you want.
 6. To save the changes, select Update.

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

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