Security Update for Microsoft Office Online Server and Office Web Apps (September 2017)

This script is Copyright (C) 2017 Tenable Network Security, Inc.


Synopsis :

An application installed on the remote Windows host is affected by
multiple remote code execution vulnerabilities.

Description :

The Microsoft Office Online Server or Microsoft Office Web
Apps installation on the remote host is missing security
updates. It is, therefore, affected by multiple
vulnerabilities :

- A remote code execution vulnerability exists in
Microsoft Office software when it fails to properly
handle objects in memory. An attacker who successfully
exploited the vulnerability could use a specially
crafted file to perform actions in the security context
of the current user. For example, the file could then
take actions on behalf of the logged-on user with the
same permissions as the current user. Exploitation of
this vulnerability requires that a user open a specially
crafted file with an affected version of Microsoft
Office software. In an email attack scenario, an
attacker could exploit the vulnerability by sending the
specially crafted file to the user and convincing the
user to open the file. In a web-based attack scenario,
an attacker could host a website (or leverage a
compromised website that accepts or hosts user-provided
content) that contains a specially crafted file that is
designed to exploit the vulnerability. However, an
attacker would have no way to force the user to visit
the website. Instead, an attacker would have to convince
the user to click a link, typically by way of an
enticement in an email or Instant Messenger message, and
then convince the user to open the specially crafted
file. The security update addresses the vulnerability by
correcting how Microsoft Office handles files in memory.
(CVE-2017-8631)

- A remote code execution vulnerability exists in
Microsoft Office software when the software fails to
properly handle objects in memory. An attacker who
successfully exploited the vulnerability could run
arbitrary code in the context of the current user. If
the current user is logged on with administrative user
rights, an attacker could take control of the affected
system. An attacker could then install programs; view,
change, or delete data; or create new accounts with full
user rights. Users whose accounts are configured to have
fewer user rights on the system could be less impacted
than users who operate with administrative user rights.
Exploitation of the vulnerability requires that a user
open a specially crafted file with an affected version
of Microsoft Office software. In an email attack
scenario, an attacker could exploit the vulnerability by
sending the specially crafted file to the user and
convincing the user to open the file. In a web-based
attack scenario, an attacker could host a website (or
leverage a compromised website that accepts or hosts
user-provided content) that contains a specially crafted
file designed to exploit the vulnerability. An attacker
would have no way to force users to visit the website.
Instead, an attacker would have to convince users to
click a link, typically by way of an enticement in an
email or instant message, and then convince them to open
the specially crafted file. Note that the Preview Pane
is not an attack vector for this vulnerability. The
security update addresses the vulnerability by
correcting how Office handles objects in memory.
(CVE-2017-8742, CVE-2017-8743)

- A remote code execution vulnerability exists due to the
way Windows Uniscribe handles objects in memory. An
attacker who successfully exploited this vulnerability
could take control of the affected system. An attacker
could then install programs; view, change, or delete
data; or create new accounts with full user rights.
Users whose accounts are configured to have fewer user
rights on the system could be less impacted than users
who operate with administrative user rights. There are
multiple ways an attacker could exploit this
vulnerability: In a web-based attack scenario, an
attacker could host a specially crafted website designed
to exploit this vulnerability and then convince a user
to view the website. An attacker would have no way to
force users to view the attacker-controlled content.
Instead, an attacker would have to convince users to
take action, typically by getting them to click a link
in an email or instant message that takes users to the
attacker's website, or by opening an attachment sent
through email. In a file-sharing attack scenario, an
attacker could provide a specially crafted document file
designed to exploit this vulnerability and then convince
a user to open the document file.The security update
addresses the vulnerability by correcting how Windows
Uniscribe handles objects in memory. (CVE-2017-8696)

See also :

http://www.nessus.org/u?8f1bdca6
http://www.nessus.org/u?ab979819
http://www.nessus.org/u?75d14528
https://portal.msrc.microsoft.com/en-us/security-guidance/summary

Solution :

Microsoft has released a set of patches for Microsoft Office Online
Server, Office Web Apps Server 2013, Office 2010 Web Apps, and Office
2013 Web Apps.

Risk factor :

High / CVSS Base Score : 9.3
(CVSS2#AV:N/AC:M/Au:N/C:C/I:C/A:C)
CVSS Temporal Score : 6.9
(CVSS2#E:U/RL:OF/RC:C)
Public Exploit Available : false

Family: Windows : Microsoft Bulletins

Nessus Plugin ID: 103192 ()

Bugtraq ID: 100741
100746
100751
100780

CVE ID: CVE-2017-8631
CVE-2017-8696
CVE-2017-8742
CVE-2017-8743

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