ESB-2017.2503 - [Cisco] Cisco Firepower Detection Engine: Denial of service - Remote/unauthenticated 2017-10-05

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             AUSCERT External Security Bulletin Redistribution

                               ESB-2017.2503
          Cisco Firepower Detection Engine SSL Decryption Memory
                Consumption Denial of Service Vulnerability
                              5 October 2017

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           Cisco Firepower Detection Engine
Publisher:         Cisco Systems
Operating System:  Cisco
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2017-12245  

Original Bulletin: 
   https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20171004-ftd

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Cisco Firepower Detection Engine SSL Decryption Memory Consumption Denial of 
Service Vulnerability

High

Advisory ID:
cisco-sa-20171004-ftd

First Published:
2017 October 4 16:00 GMT

Version 1.0:
Final

Workarounds:
No workarounds available

Cisco Bug IDs:
CSCve02069

CVSS Score:
Base 8.6

CVE-2017-12245
CWE-399

Summary

A vulnerability in SSL traffic decryption for Cisco Firepower Threat Defense 
(FTD) Software could allow an unauthenticated, remote attacker to cause 
depletion of system memory. If this memory leak persists over time, a denial 
of service (DoS) condition could develop because traffic can cease to be 
forwarded through the device.

The vulnerability is due to an error in how the Firepower Detection Snort 
Engine handles SSL traffic decryption and notifications to and from the 
Adaptive Security Appliance (ASA) handler. An attacker could exploit this 
vulnerability by sending a steady stream of malicious Secure Sockets Layer 
(SSL) traffic through the device. An exploit could allow the attacker to cause
a DoS condition when the device runs low on system memory.

Cisco has released software updates that address this vulnerability. There are
no workarounds that address this vulnerability.

This advisory is available at the following link:

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20171004-ftd

Affected Products

Vulnerable Products

This vulnerability affects Cisco Firepower Threat Defense (FTD) Software 
Releases 6.0.1 and later when the software is configured as described in this
section and is running on any of the following Cisco products:

    Adaptive Security Appliance (ASA) 5500-X Series Next-Generation Firewalls
    Firepower 2100 Series Security Appliances
    Firepower 4100 Series Security Appliances
    Firepower 9300 Series Security Appliances

Affected devices are vulnerable when they are configured for one or more SSL 
inspection policies for Decrypt and Resign or Known Key. These features allow
the SSL traffic to be decrypted on the device for further inspection.

This vulnerability applies to FTD-supported releases only. These releases 
contain both Firepower and ASA code. Review Firepower Threat Defense Devices 
in the Cisco Firepower Compatibility Guide for additional information.

Administrators can use the CLI command show version to determine the FTD 
release. In this example, the device is running 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

No other Cisco products are currently known to be affected by this 
vulnerability.

Cisco has confirmed that this vulnerability does not affect the following 
Cisco products:

    3000 Series Industrial Security Appliances (ISA)
    Adaptive Security Appliance (ASA) 5000-X Series with FirePOWER Services
    Adaptive Security Appliance (ASA) 5500-X Series with FirePOWER Services
    Advanced Malware Protection (AMP) for Networks, 7000 Series Appliances
    Advanced Malware Protection (AMP) for Networks, 8000 Series Appliances
    FirePOWER 7000 Series Appliances
    FirePOWER 8000 Series Appliances
    Firepower Management Center
    Firepower Threat Defense for Integrated Services Routers (ISRs)
    Intrusion Prevention System (IPS) Software
    Virtual Next-Generation Intrusion Prevention System (NGIPSv) for VMware

Details

Cisco FTD is a unified software image that includes the ASA features and 
Firepower services. This unified software is capable of offering the function
of ASA and Firepower in one platform, both in terms of hardware and software 
features.

Indicators of Compromise

Vulnerable devices are compromised when all the following conditions are met:

The device stops forwarding traffic.

The output of the show blocks command shows a zero count of a particular 
memory block. This is most common for the memory blocks of size 2048 or 9344.

    firepower# show blocks
      SIZE    MAX    LOW    CNT
         0   1450   1448   1450
         4    100     99     99
        80   1000    950    984
       256   4148   3898   4040
      1550   6279   6184   6258
      2048    15864    0      0
      2560    164    164    164
      4096    100    100    100
      8192    100    100    100
      9344    100    100    100
     16384    102    102    102
     65536     16     16     16


    The output of the debug command show asp inspect-dp snort queues detail 
    debug shows the Receive Queue UtilizationRxQ (util)at 100 percent.

    firepower# show asp inspect-dp snort queues detail debug
    SNORT Inspect Instance Queue Configuration

    RxQ-Size:              1   MB  
    TxQ-Size:            128   KB
    TxQ-Data-Limit:      102.4 KB   (80%)
    TxQ-Data-Hi-Thresh:   35.8 KB   (28%)
    Id QId  RxQ        RxQ    RxQ        RxQ              TxQ        TxQ    TxQ        TxQ              
           (used)     (util) (max used) (state)          (used)     (util) (max used) (state)          
    -- ---- ---------- ------ ---------- ---------------- ---------- ------ ---------- -------- 
    0  [0]    2   MB   100%     2   MB   READY              0        0%       2.1 KB   READY


    The output of the debug command show asp inspect-dp snort counters debug 
    zeros shows a count for Receive Queue Full (RxQ-Full) that is not zero.

    firepower# show asp inspect-dp snort counters debug zeros SNORT Inspect 
    Instance Counters

    Id   QId  Type  Name                           Value      Raw-Value
    --   ---- ----  ----                           ---------- ----------
    ...
    All  All  drop  RxQ-Full                       146.5 K    (146546)
    All  All  drop  TxQ-Full                         0        (0)

Contact the Cisco Technical Assistance Center (TAC) if additional assistance 
is required to determine whether the device has been compromised by 
exploitation of this vulnerability.

Workarounds

There are no workarounds that address this vulnerability.

Fixed Software

Cisco has released free software updates that address the vulnerability 
described in this advisory. Customers may only install and expect support for
software versions and feature sets for which they have purchased a license. By
installing, downloading, accessing, or otherwise using such software upgrades,
customers agree to follow the terms of the Cisco software license: 
https://www.cisco.com/c/en/us/products/end-user-license-agreement.html

Additionally, customers may only download software for which they have a valid
license, procured from Cisco directly, or through a Cisco authorized reseller
or partner. In most cases this will be a maintenance upgrade to software that
was previously purchased. Free security software updates do not entitle 
customers to a new software license, additional software feature sets, or 
major revision upgrades.

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 TAC 
or their contracted maintenance providers.

Customers Without Service Contracts

Customers who purchase directly from Cisco but do not hold a Cisco service 
contract and customers who make purchases through third-party vendors but are
unsuccessful in obtaining fixed software through their point of sale should 
obtain upgrades by contacting the Cisco TAC: 
https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html

Customers should have the product serial number available and be prepared to 
provide the URL of this advisory as evidence of entitlement to a free upgrade.

Fixed Releases

Customers should upgrade to an appropriate release as indicated in the table 
in this section. To help ensure a complete upgrade solution, consider that 
this advisory is part of a collection that includes the following advisories:

    cisco-sa-20171004-fpsnort: Cisco Firepower Detection Engine IPv6 Denial of
    Service Vulnerability

    cisco-sa-20171004-ftd: Cisco Firepower Detection Engine SSL Decryption 
    Memory Consumption Denial of Service Vulnerability

In the following table, the left column lists major releases of Cisco 
software. The center column indicates whether a major release is affected by 
the vulnerability described in this advisory and the first minor release that
includes the fix for this vulnerability. The right column indicates whether a
major release is affected by all the vulnerabilities described in this 
collection of advisories and the current recommended release for those 
vulnerabilities.

****

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

This vulnerability was found during resolution of a Cisco TAC support case.

URL

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20171004-ftd

Revision History

Version Description 		Section 	Status 	Date 
1.0 	Initial public release. -		Final 	2017-October-04

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