ESB-2018.0688 - [Cisco] Cisco Web Security Appliance: Execute arbitrary code/commands - Remote/unauthenticated 2018-03-09

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             AUSCERT External Security Bulletin Redistribution

                               ESB-2018.0688
   Cisco Web Security Appliance FTP Authentication Bypass Vulnerability
                               9 March 2018

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

Product:           Cisco Web Security Appliance
Publisher:         Cisco Systems
Operating System:  Cisco
Impact/Access:     Execute Arbitrary Code/Commands -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2018-0087  

Original Bulletin: 
   https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180307-wsa

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Cisco Security Advisory

Cisco Web Security Appliance FTP Authentication Bypass Vulnerability

High

Advisory ID:
cisco-sa-20180307-wsa

First Published:
2018 March 7 16:00 GMT

Version 1.0:
Final

Workarounds:
No workarounds available

Cisco Bug IDs:
CSCvf74281
CVE-2018-0087
CWE-287

CVSS Score:
Base 7.3
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L/E:X/RL:X/RC:X
CVE-2018-0087
CWE-287

Summary

A vulnerability in the FTP server of the Cisco Web Security Appliance (WSA)
could allow an unauthenticated, remote attacker to log in to the FTP server of
the device without a valid password. The attacker does need to have a valid
username.
The vulnerability is due to incorrect FTP user credential validation. An
attacker could exploit this vulnerability by using FTP to connect to the
management IP address of the targeted device. A successful exploit could allow
the attacker to log in to the FTP server of the Cisco WSA without having a
valid password.
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-20180307-wsa

Affected Products

Vulnerable Products

This vulnerability affects Cisco AsyncOS for WSA Software on both virtual and
hardware appliances that are running any release of Cisco AsyncOS 10.5.1 for
WSA Software. See the Fixed Software section of this security advisory for
additional information about the affected software releases.
The device is vulnerable only if FTP is enabled on the management interface.
FTP is disabled by default.
Determining Whether FTP Is Configured
An administrator can determine whether FTP is configured on the management
interface by using one of the following three methods.
First Method to Determine Whether FTP Is Configured
The administrator can issue the showconfig command and check whether the ftpd
port is configured on the management interface.
ciscowsa> showconfigChoose the password option:1. Mask passwords (Files with
masked passwords cannot be loaded using loadconfig command)2. Plain
passphrases[1]> 1... <interfaces> <interface>
<interface_name>Management</interface_name> <ip>x.x.x.x</ip>
<phys_interface>Management</phys_interface> <netmask>24</netmask>
<interface_hostname>xxx.xxx.xxx</interface_hostname>
<ftpd_port>21</ftpd_port>...
Second Method to Determine Whether FTP Is Configured
The administrator can check the FTP configuration by issuing the ifconfig
command. In this example, the management interface is configured for FTP. The
Y value in square brackets represents the current configuration.
ciscowsa> ifconfig...Choose the operation you want to perform:- NEW - Create a
new interface.- EDIT - Modify an interface.- DELETE - Remove an interface.-
DETAILS - Show details of an interface.> EDITEnter the number of the interface
you wish to edit.[]> 1..Do you want to enable FTP on this interface? [Y]>...
Third Method to Determine Whether FTP Is Configured
The administrator can also use the GUI to check the FTP configuration by
navigating to Network > Interfaces > Appliance Management Services and
determining whether the FTP check box is checked.
Determining the WSA Software Release
To determine whether a vulnerable release of Cisco AsyncOS Software is running
on a Cisco WSA, administrators can use the version command in the WSA CLI. The
following example shows the results for an appliance that is running Cisco
AsyncOS Software Release 10.5.1-296:
ciscowsa> versionCurrent Version===============Product: Cisco IronPort S670
Web Security ApplianceModel: S670Version: 10.5.1-296...

Products Confirmed Not Vulnerable

No other Cisco products are currently known to be affected by this
vulnerability.
The following products are not affected by this vulnerability:
 Email Security Appliance (ESA), both virtual and hardware versions
 Security Mail Appliance (SMA), both virtual and hardware versions

Workarounds

There are no workarounds that address this vulnerability. However, this
vulnerability exists only when FTP is enabled on the management interface. If
FTP is disabled, this vulnerability does not exist; therefore, disabling FTP
is considered a mitigation for the vulnerability.
Disabling FTP on the Management Interface
An administrator can disable FTP on the management interface by using one of
the following two methods.
First Method to Disable FTP on the Management Interface
The administrator can disable FTP by issuing the ifconfig command to edit the
management interface configuration and then issuing the commit command to
commit the change.
ciscowsa> ifconfig...Choose the operation you want to perform:- NEW - Create a
new interface.- EDIT - Modify an interface.- DELETE - Remove an interface.-
DETAILS - Show details of an interface.> EDITEnter the number of the interface
you wish to edit.[]> 1..Do you want to enable FTP on this interface? [Y]>
N...Choose the operation you want to perform:- NEW - Create a new interface.-
EDIT - Modify an interface.- DELETE - Remove an interface.- DETAILS - Show
details of an interface.[]> ciscowsa> commitWarning: In order to process these
changes, the proxy process will restart after Commit. This will cause a brief
interruption in service. Additionally, the authentication cache will be
cleared, which might require some users to authenticate again.Warning:
Processing of network configuration changes might cause a brief interruption
in network availability.Please enter some comments describing your changes:[]>
disable FTPChanges committed...
Second Method to Disable FTP on the Management Interface
The administrator can disable FTP from the GUI by navigating to Network >
Interfaces > Appliance Management Services and unchecking the FTP check box,
then clicking Submit to commit the change.

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:
http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.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
Technical Assistance Center (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:
http://www.cisco.com/en/US/support/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

In the following table, the left column lists major releases of Cisco AsyncOS
for WSA Software. The right 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.
Customers should upgrade to an appropriate release as indicated in the
following table:
Cisco AsyncOS for WSA Software Major Release
First Fixed Release for This Advisory
Prior to 10.5.1
Not vulnerable
10.5.1
10.5.2-042 or later
11.0 and later
Not vulnerable
In most cases, a WSA can be updated over the network by using the System
Upgrade options in the System Administration GUI. Administrators can use the
following steps to upgrade a device by using the System Administration GUI:

 Choose System Administration > System Upgrade.

 Click Upgrade Options.

 Choose Download and Install.

 Choose the release to upgrade to.

 In the Upgrade Preparation area, choose the appropriate options.

 Click Proceed to begin the upgrade. A progress bar displays the status of the
 upgrade.
 
 After the upgrade is complete, the device reboots.

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.

Cisco Security Vulnerability Policy

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

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180307-wsa

Revision History

Version	Description		Section	Status	Date
1.0	Initial public release.		Final	2018-March-07

Legal Disclaimer

THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF
GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS
FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS
LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO
CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.
A standalone copy or paraphrase of the text of this document that omits the
distribution URL is an uncontrolled copy and may lack important information or
contain factual errors. The information in this document is intended for end
users of Cisco products.

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