Summary

• A vulnerability in the email filtering functionality of Cisco AsyncOS Software for Cisco Email Security Appliances could allow an unauthenticated, remote attacker to bypass Advanced Malware Protection (AMP) filters that are configured for an affected device.
  
  The vulnerability is due to improper error handling when malformed Multipurpose Internet Mail Extensions (MIME) headers are present in an email attachment that is sent through an affected device. An attacker could exploit this vulnerability by sending an email message that has a crafted, MIME-encoded file attachment through an affected device. A successful exploit could allow the attacker to bypass AMP filter configurations for the device.
  
  There are no workarounds that address this vulnerability.
  
  This advisory is available at the following link:
  https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20161116-esa1

Affected Products

• Vulnerable Products

  This vulnerability affects all releases prior to the first fixed release of Cisco AsyncOS Software for both virtual and hardware versions of Cisco Email Security Appliances, if the AMP feature is configured to scan incoming email attachments.
  
  To determine whether AMP is configured on a Cisco Email Security Appliance (ESA), administrators can use the Cisco AsyncOS System Administration GUI or the command-line interface (CLI).
  
  In the System Administration GUI, choose Security Services > File Reputation and Analysis, and then check the setting for the File Reputation option.
  
  In the CLI, issue the ampconfig command and check the value of the File Reputation field in the command output. The following example shows the output of the ampconfig command for an ESA that has AMP configured to scan incoming email attachments:

  ciscoesa> ampconfig
  
  File Reputation: Enabled
  File Analysis: Enabled
  File types selected for File Analysis:
       Microsoft Windows / DOS Executable
  Appliance Group ID/Name: Not part of any group yet

  To determine which release of Cisco AsyncOS Software is running on an ESA, administrators can use the version command in the CLI. The following example shows the output of the version command for an ESA running Cisco AsyncOS Software Release 8.5.7-044:

  ciscoesa> version
  
  Current Version
  ===============
  Product: Cisco IronPort X1070 Messaging Gateway(tm) Appliance
  Model: X1070
  Version: 8.5.7-044
  .
  .
  .

  Note that Cisco provides regular maintenance of products in the Cisco Cloud Email Security (CES) service solution, which includes Cisco Email Security Appliances and Cisco Content Security Management Appliances. Customers can also request a software upgrade by contacting Cisco CES support.

  Products Confirmed Not Vulnerable

  No other Cisco products are currently known to be affected by this vulnerability.
  
  Cisco has confirmed that this vulnerability does not affect the following products:
  

  • Cisco Content Security Management Appliance, virtual and hardware versions
  • Cisco Web Security Appliance, virtual and hardware versions

Workarounds

• There are no workarounds that address this vulnerability.

Fixed Software

• For information about fixed software releases, consult the Cisco bug ID at the top of this advisory.
  
  When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories and Alerts page, to determine exposure and a complete upgrade solution.
  
  In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.

Exploitation and Public Announcements

• The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20161116-esa1

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	—	Final	2016-November-16

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