BugTraq
Bomgar Remote Support - Local Privilege Escalation (CVE-2017-5996) Oct 26 2017 05:58PM
VSR Advisories (advisories vsecurity com)

                   Virtual Security Research, LLC.
                      https://www.vsecurity.com/
                          Security Advisory

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Advisory Name: Bomgar Remote Support - Local Privilege Escalation
 Release Date: 2017-10-26
  Application: Bomgar Remote Support
     Versions: 15.2.x before 15.2.3
               16.1.x before 16.1.5
               16.2.x before 16.2.4
     Severity: High/Medium
       Author: Robert Wessen <rwessen (a) vsecurity . com>
       Author: Mitch Kucia <mkucia (a) vsecurity . com>
Vendor Status: Update Released [2]
CVE Candidate: CVE-2017-5996
    Reference: https://www.vsecurity.com/download/advisories/20171026-1.txt

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Product Description
~-----------------~
From Bomgar's website [1]: "The fastest, most secure way for experts to access
and support the systems that need them."

Vulnerability Overview
~--------------------~
In mid-January, VSR identified a privilege escalation vulnerability in Bomgar
Remote Support application which can be used to escalate from any unprivileged
user to nt authority/system on Microsoft Windows 7 systems. The vulnerability
originates from an nt authority/system service being executed from a folder
with excessive permissions. The exploit requires a remote support agent to log
into the affected system.

Vulnerability Details
~-------------------~
The Bomgar Remote Support agent enables remote support personnel to establish
screen sharing, access command shell, and perform system administration tasks
on machines with the agent installed. The agent, by default, creates a service
as the Windows LocalSystem account and creates a folder at
C:\ProgramData\bomgar-ssc-0xhhhhhhhh (where each h is a hex character). The
agent is also executed from this folder, so the folder is included in the
Windows dynamic library loader search path. The default permissions on the
C:\ProgramData folder allow all users, even unprivileged ones, to append and
write files. These permissions are inherited by sub-directories unless
explicitly overridden. These permissions are not changed during the
installation of the agent, so a DLL planting/hijack is possible.

A Trojan horse with the same name as one of the requested, but not present
libraries can be placed inside the C:\ProgramData\bomgar-ssc-0xhhhhhhhh folder
since this folder is writeable by all users. When a remote support person
attempts to connect to the host, the malicious library will be loaded and code
can executed as nt authority/system.

Versions Affected
~---------------~
The issue was originally discovered in version 16.1.1, although it likely
exists since at least version 14. All testing was performed exclusively on
Windows 7, however the vulnerability is suspected to be present on all
supported Windows platforms.

Vendor Response
~-------------~
The following timeline details Bomgar's response to the reported issue:

2017-02-05    VSR contacted Bomgar via several public email addresses to file a
              security report.

2017-02-06    Bomgar replied, VSR provided additional details on the
              vulnerability and Bomgar began internal triage.

2017-02-13    Bomgar confirmed reproduction and indicated a hotfix will be
              available to select customers on 2017-02-17. Patch for all
              customers will be available at a later date.

2017-03-28    Bomgar releases patch in Remote Support versions 15.2.3 [2],
              16.1.5 [3], and 16.2.4 [4].

2017-10-26    VSR advisory released.

Recommendation
~------------~
Upgrade all client installs to the latest version of Bomgar Remote Support
software as soon as possible.

Common Vulnerabilities and Exposures (CVE) Information
~----------------------------------------------------~
The Common Vulnerabilities and Exposures (CVE) project has assigned
the number CVE-2017-5996 to this issue. This is a candidate for
inclusion in the CVE list (https://cve.mitre.org), which standardizes
names for security problems.

Acknowledgments
~--------------~
Thanks to the Bomgar development team for a prompt response, confirmation, and
patch.

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References:

1. https://www.bomgar.com/

2. https://www.bomgar.com/support/changelog/remote-support-15-2-3

3. https://www.bomgar.com/support/changelog/remote-support-16-1-5

4. https://www.bomgar.com/support/changelog/remote-support-1624

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This advisory is distributed for educational purposes only with the sincere
hope that it will help promote public safety.  This advisory comes with
absolutely NO WARRANTY; not even the implied warranty of merchantability or
fitness for a particular purpose.  Neither Virtual Security Research, LLC nor
the author accepts any liability for any direct, indirect, or consequential
loss or damage arising from use of, or reliance on, this information.

See the VSR disclosure policy for more information on our responsible
disclosure practices:
  https://www.vsecurity.com/company/disclosure

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     Copyright 2017 Virtual Security Research, LLC.  All rights reserved.

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