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             AUSCERT External Security Bulletin Redistribution

                    OpenSSL vulnerability CVE-2020-1968
                              4 January 2021


        AusCERT Security Bulletin Summary

Product:           BIG-IP
Publisher:         F5 Networks
Operating System:  Network Appliance
Impact/Access:     Access Privileged Data -- Remote/Unauthenticated
Resolution:        Mitigation
CVE Names:         CVE-2020-1968  

Reference:         ESB-2020.4298

Original Bulletin: 

Revision History:  January   4 2021: Additional mitigation instructions added by vendor
                   December 11 2020: Initial Release

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K92451315: OpenSSL vulnerability CVE-2020-1968

Original Publication Date: 11 Dec, 2020
Latest   Publication Date: 29 Dec, 2020

Security Advisory Description

The Raccoon attack exploits a flaw in the TLS specification which can lead to
an attacker being able to compute the pre-master secret in connections which
have used a Diffie-Hellman (DH) based ciphersuite. In such a case this would
result in the attacker being able to eavesdrop on all encrypted communications
sent over that TLS connection. The attack can only be exploited if an
implementation re-uses a DH secret across multiple TLS connections. Note that
this issue only impacts DH ciphersuites and not ECDH ciphersuites. This issue
affects OpenSSL 1.0.2 which is out of support and no longer receiving public
updates. OpenSSL 1.1.1 is not vulnerable to this issue. Fixed in OpenSSL 1.0.2w
(Affected 1.0.2-1.0.2v). (CVE-2020-1968)


An attacker may be able to exploit OpenSSL Transport Layer Security (TLS),
which allows unauthorized exposure of information when Diffie-Hellman (DH)
secrets are reused across multiple TLS connections.

Security Advisory Status

F5 Product Development has assigned ID 945421 (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.

|                  |      |Versions  |Fixes     |          |CVSSv3|Vulnerable |
|Product           |Branch|known to  |introduced|Severity  |score^|component  |
|                  |      |be        |in        |          |1     |or feature |
|                  |      |vulnerable|          |          |      |           |
|                  |16.x  |16.0.0 -  |None      |          |      |           |
|                  |      |16.0.1    |          |          |      |           |
|                  +------+----------+----------+          |      |           |
|                  |15.x  |15.1.0 -  |None      |          |      |           |
|                  |      |15.1.2    |          |          |      |           |
|BIG-IP (LTM, AAM, +------+----------+----------+          |      |           |
|Advanced WAF, AFM,|14.x  |14.1.0 -  |None      |          |      |TLS        |
|Analytics, APM,   |      |14.1.3    |          |          |      |connections|
|ASM, DDHD, DNS,   +------+----------+----------+Medium    |5.9   |(OpenSSL,  |
|FPS, GTM, Link    |13.x  |13.1.0 -  |None      |          |      |SSL        |
|Controller, PEM,  |      |13.1.3    |          |          |      |profiles)  |
|SSLO)             +------+----------+----------+          |      |           |
|                  |12.x  |12.1.0 -  |None      |          |      |           |
|                  |      |12.1.5    |          |          |      |           |
|                  +------+----------+----------+          |      |           |
|                  |11.x  |11.6.1 -  |None      |          |      |           |
|                  |      |11.6.5    |          |          |      |           |
|                  |7.x   |None      |Not       |          |      |           |
|                  |      |          |applicable|          |      |           |
|                  +------+----------+----------+          |      |           |
|BIG-IQ Centralized|6.x   |None      |Not       |Not       |None  |None       |
|Management        |      |          |applicable|vulnerable|      |           |
|                  +------+----------+----------+          |      |           |
|                  |5.x   |None      |Not       |          |      |           |
|                  |      |          |applicable|          |      |           |
|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.

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 disable DH ciphersuites key exchanges
in the vulnerable components. The Elliptic Curve Diffie-Hellman (ECDH)
ciphersuites exchanges are not affected. To disable the DH ciphersuites in the
SSL profile, perform the following procedure:

Impact of procedure: Performing the following procedure should not have a
negative impact on your system. The changes take effect when you associate the
new SSL profile to a virtual server.

 1. Log in to the Configuration utility.
 2. Go to Local Traffic > Profiles > SSL > Client.
 3. Select Create to create a new profile.
 4. For the new profile, under General Properties, enter a name.
 5. Set Configuration to Advanced.
 6. For Ciphers, select the Custom check box.
 7. For Ciphers, select Cipher Suites.

    Note: In BIG-IP 13.x, select Cipher String. In BIG-IP 11.x - 12.x, skip
    this step.

 8. For Ciphers, enter a cipher string.

    For example, to disable the TLSv1 protocol and DHE ciphers, use the
    following syntax:


 9. Configure the remaining profile settings.
10. Select Finished.

For more information on configuring ciphers on SSL profiles, refer to K13171:
Configuring the cipher strength for SSL profiles (11.x)

Supplemental Information

o K41942608: Overview of security advisory articles
  o K91158923: BIG-IP SSL/TLS ADH/DHE vulnerability CVE-2020-5929
  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 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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