Summary

• A vulnerability in the TCP syslog module of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to exhaust the 1550-byte buffers on an affected device, resulting in a denial of service (DoS) condition.
  
  The vulnerability is due to a missing boundary check in an internal function. An attacker could exploit this vulnerability by establishing a man-in-the-middle position between an affected device and its configured TCP syslog server and then maliciously modifying the TCP header in segments that are sent from the syslog server to the affected device. A successful exploit could allow the attacker to exhaust buffer on the affected device and cause all TCP-based features to stop functioning, resulting in a DoS condition. The affected TCP-based features include AnyConnect SSL VPN, clientless SSL VPN, and management connections such as Secure Shell (SSH), Telnet, and HTTPS.

  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-20181003-asa-syslog-dos

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software. For information about affected software releases, consult the Cisco bug ID(s) at the top of this advisory.

  Determine the Cisco ASA Software Release

  To determine which Cisco ASA Software release is running on a device, administrators can log in to the device, use the show version command in the CLI, and refer to the output of the command. The following example shows the output of the command for a device that is running Cisco ASA Software Release 9.4(4):

  ciscoasa# show version | include Version
  
  Cisco Adaptive Security Appliance Software Version 9.4(4)
  Device Manager Version 7.4(1)
  .
  .
  .

  If a device is managed by using Cisco Adaptive Security Device Manager (ASDM), administrators can also determine which release is running on a device by referring to the release information in the table that appears in the Cisco ASDM log in window or the Device Dashboard tab of the Cisco ASDM Home pane.

  Determine the Cisco FTD Software Release

  To determine which Cisco FTD Software release is running on a device, administrators can log in to the device, use the show version command in the CLI, and refer to the output of the command. The following example shows the output of the command for a device that is running Cisco FTD Software Release 6.2.0:

  > show version
  
  ---------------------[ ftd ]---------------------
  Model : Cisco ASA5525-X Threat Defense (75) Version 6.2.0 (Build 362)
  UUID : 2849ba3c-ecb8-11e6-98ca-b9fc2975893c
  Rules update version : 2017-03-15-001-vrt
  VDB version : 279
  ----------------------------------------------------

  Products Confirmed Not Vulnerable

  Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.

Workarounds

• There are no workarounds that address this vulnerability.

Fixed Software

• For information about fixed software releases, consult the Cisco bug ID(s) 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.

Source

• Cisco would like to thank J-M Roth for reporting this vulnerability.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20181003-asa-syslog-dos

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2018-October-03

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