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             AUSCERT External Security Bulletin Redistribution

     The BIG-IP SMTPS virtual server may fail to properly restrict I/O
           buffering, allowing attackers to insert commands into
                          encrypted SMTP sessions
                               25 March 2019


        AusCERT Security Bulletin Summary

Product:           F5 BIG-IP products
Publisher:         F5 Networks
Operating System:  Network Appliance
Impact/Access:     Execute Arbitrary Code/Commands -- Remote/Unauthenticated
Resolution:        Patch/Upgrade

Original Bulletin: 

Revision History:  March 25 2019: Updated to include latest revision
                   March 22 2019: Initial Release

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K23284054:The BIG-IP SMTPS virtual server may fail to properly restrict I/O buffering, allowing attackers to insert commands into encrypted SMTP sessions

Security Advisory

Original Publication Date: 22 Mar, 2019

Latest   Publication Date: 23 Mar, 2019

Security Advisory Description

This issue occurs the following condition is met:

  o A virtual server is configured with a Client SSL profile and an SMTPS
    profile that has the STARTTLS Activation Mode setting enabled (Allow or
    Require) for processing SMTPS traffic.


When system receives these SMTP commands are received as a group, the affected
SMTPS virtual server improperly processes the SMTP commands after the STARTTLS
command. As a result, an attacker may be able to inject commands into the
encrypted session. Per RFC3207, if an SMTP client uses command pipelining, the
STARTTLS command must be the last command in the group.  


As a result of this issue, you may encounter the following symptom:

  o When the STARTTLS command and SMTP commands are sent in a group, the system
    accepts and processes the SMTP commands while still waiting for the client
    to start the Transport Layer Security (TLS) negotiation.

Security Advisory Status

F5 Product Development has assigned ID 610138 to this issue. F5 has confirmed
that this issue exists in the products listed in the Applies to (see versions)
box, located in the upper-right corner of this article. For information about
releases, point releases, or hotfixes that resolve this issue, refer to the
following table.

|Type of fix       |Fixes introduced  |Related articles                       |
|                  |in                |                                       |
|                  |13.1.0            |                                       |
|Release           |12.1.4            |K2200: Most recent versions of F5      |
|                  |11.6.4            |software                               |
|                  |11.5.9            |                                       |
|Point release/    |None              |None                                   |
|hotfix            |                  |                                       |

Security Advisory Recommended Actions



Supplemental Information

o K51812227: Understanding Security Advisory versioning
  o K41942608: Overview of AskF5 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 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 RFC3207: SMTP Service Extension for Secure SMTP over Transport Layer

    Note: This link takes you to a resource outside of AskF5, and it is
    possible that the document may be removed without our knowledge.

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