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             AUSCERT External Security Bulletin Redistribution

                               ESB-2019.0355
    Cisco Web Security Appliance Decryption Policy Bypass Vulnerability
                              7 February 2019

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

Product:           Cisco Web Security Appliance
Publisher:         Cisco Systems
Operating System:  Cisco
Impact/Access:     Unauthorised Access -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2019-1672  

Original Bulletin: 
   https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190206-wsa-bypass

- --------------------------BEGIN INCLUDED TEXT--------------------

Cisco Security Advisory

Cisco Web Security Appliance Decryption Policy Bypass Vulnerability

Advisory ID:      cisco-sa-20190206-wsa-bypass
First Published:  2019 February 6 16:00 GMT
Version 1.0:      Final
Workarounds:      No workarounds available
Cisco Bug IDs:    CSCvm91630
                  CVE-2019-1672
                  CWE-400
CVSS Score:       Base 5.8
CVSS:             3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N/E:X/RL:X/RC:X

Summary

  o
    A vulnerability in the Decryption Policy Default Action functionality of
    the Cisco Web Security Appliance (WSA) could allow an unauthenticated,
    remote attacker to bypass a configured drop policy and allow traffic onto
    the network that should have been denied.

    The vulnerability is due to the incorrect handling of SSL-encrypted traffic
    when Decrypt for End-User Notification is disabled in the configuration. An
    attacker could exploit this vulnerability by sending a SSL connection
    through the affected device. A successful exploit could allow the attacker
    to bypass a configured drop policy to block specific SSL connections.

    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-20190206-wsa-bypass

Affected Products

  o Vulnerable Products

    This vulnerability affects Cisco Web Security Appliance. For information
    about affected software releases, consult the Cisco bug ID(s) at the top of
    this advisory.

    Products Confirmed Not Vulnerable

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

Details

  o To determine if Decrypt for End-User Notification is Disabled on the WSA,
    an administrator can do the following:

      - Navigate to Security Service > HTTPS Proxy > Decrypt for End-User
        Notification.
      - Verify that the Decrypt for End-User Notification configuration setting
        is Disabled.

Workarounds

  o There are no workarounds that address this vulnerability.

Fixed Software

  o 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

  o 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

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

Cisco Security Vulnerability Policy

  o To learn about Cisco security vulnerability disclosure policies and
    publications, see the Security Vulnerability Policy. This document also
    contains instructions for obtaining fixed software and receiving security
    vulnerability information from Cisco.

URL

  o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
    cisco-sa-20190206-wsa-bypass

Revision History

  o
    +---------+---------------------------+---------+--------+-------------------+
    | Version |        Description        | Section | Status |       Date        |
    +---------+---------------------------+---------+--------+-------------------+
    | 1.0     | Initial public release.   | --       | Final  | 2019-February-06 |
    +---------+---------------------------+---------+--------+-------------------+

- --------------------------END INCLUDED TEXT--------------------

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