Vulnerabilities > CVE-2020-0695 - Improper Input Validation vulnerability in Microsoft Office Online Server

047910
CVSS 5.8 - MEDIUM
Attack vector
NETWORK
Attack complexity
MEDIUM
Privileges required
NONE
Confidentiality impact
PARTIAL
Integrity impact
PARTIAL
Availability impact
NONE
network
microsoft
CWE-20
nessus

Summary

A spoofing vulnerability exists when Office Online Server does not validate origin in cross-origin communications correctly, aka 'Microsoft Office Online Server Spoofing Vulnerability'.

Vulnerable Configurations

Part Description Count
Application
Microsoft
1

Common Weakness Enumeration (CWE)

Common Attack Pattern Enumeration and Classification (CAPEC)

  • Buffer Overflow via Environment Variables
    This attack pattern involves causing a buffer overflow through manipulation of environment variables. Once the attacker finds that they can modify an environment variable, they may try to overflow associated buffers. This attack leverages implicit trust often placed in environment variables.
  • Server Side Include (SSI) Injection
    An attacker can use Server Side Include (SSI) Injection to send code to a web application that then gets executed by the web server. Doing so enables the attacker to achieve similar results to Cross Site Scripting, viz., arbitrary code execution and information disclosure, albeit on a more limited scale, since the SSI directives are nowhere near as powerful as a full-fledged scripting language. Nonetheless, the attacker can conveniently gain access to sensitive files, such as password files, and execute shell commands.
  • Cross Zone Scripting
    An attacker is able to cause a victim to load content into their web-browser that bypasses security zone controls and gain access to increased privileges to execute scripting code or other web objects such as unsigned ActiveX controls or applets. This is a privilege elevation attack targeted at zone-based web-browser security. In a zone-based model, pages belong to one of a set of zones corresponding to the level of privilege assigned to that page. Pages in an untrusted zone would have a lesser level of access to the system and/or be restricted in the types of executable content it was allowed to invoke. In a cross-zone scripting attack, a page that should be assigned to a less privileged zone is granted the privileges of a more trusted zone. This can be accomplished by exploiting bugs in the browser, exploiting incorrect configuration in the zone controls, through a cross-site scripting attack that causes the attackers' content to be treated as coming from a more trusted page, or by leveraging some piece of system functionality that is accessible from both the trusted and less trusted zone. This attack differs from "Restful Privilege Escalation" in that the latter correlates to the inadequate securing of RESTful access methods (such as HTTP DELETE) on the server, while cross-zone scripting attacks the concept of security zones as implemented by a browser.
  • Cross Site Scripting through Log Files
    An attacker may leverage a system weakness where logs are susceptible to log injection to insert scripts into the system's logs. If these logs are later viewed by an administrator through a thin administrative interface and the log data is not properly HTML encoded before being written to the page, the attackers' scripts stored in the log will be executed in the administrative interface with potentially serious consequences. This attack pattern is really a combination of two other attack patterns: log injection and stored cross site scripting.
  • Command Line Execution through SQL Injection
    An attacker uses standard SQL injection methods to inject data into the command line for execution. This could be done directly through misuse of directives such as MSSQL_xp_cmdshell or indirectly through injection of data into the database that would be interpreted as shell commands. Sometime later, an unscrupulous backend application (or could be part of the functionality of the same application) fetches the injected data stored in the database and uses this data as command line arguments without performing proper validation. The malicious data escapes that data plane by spawning new commands to be executed on the host.

Nessus

NASL familyWindows : Microsoft Bulletins
NASL idSMB_NT_MS20_FEB_OFFICE_WEB.NASL
descriptionThe Microsoft Office Online Server installation on the remote host is missing a security update. It is, therefore, affected by the following vulnerability : - A spoofing vulnerability exists when Office Online Server does not validate origin in cross-origin communications correctly. An attacker could exploit the vulnerability by sending a specially crafted request to an affected site. The attacker who successfully exploited the vulnerability could then perform cross- origin attacks on affected systems. These attacks could allow the attacker to read content that the attacker is not authorized to read, and use the victim
last seen2020-03-18
modified2020-02-11
plugin id133621
published2020-02-11
reporterThis script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.
sourcehttps://www.tenable.com/plugins/nessus/133621
titleSecurity Updates for Microsoft Office Online Server (February 2020)
code
#
# (C) Tenable Network Security, Inc.
#


# The descriptive text and package checks in this plugin were  
# extracted from the Microsoft Security Updates API. The text
# itself is copyright (C) Microsoft Corporation.
#


include('compat.inc');

if (description)
{
  script_id(133621);
  script_version("1.5");
  script_set_attribute(attribute:"plugin_modification_date", value:"2020/03/13");

  script_cve_id("CVE-2020-0695");
  script_xref(name:"MSKB", value:"4484254");
  script_xref(name:"MSFT", value:"MS20-4484254");

  script_name(english:"Security Updates for Microsoft Office Online Server (February 2020)");

  script_set_attribute(attribute:"synopsis", value:
"The Microsoft Office Online Server installation on the remote host is missing a security update.");
  script_set_attribute(attribute:"description", value:
"The Microsoft Office Online Server installation on the
remote host is missing a security update. It is, therefore,
affected by the following vulnerability :

  - A spoofing vulnerability exists when Office Online
    Server does not validate origin in cross-origin
    communications correctly. An attacker could exploit the
    vulnerability by sending a specially crafted request to
    an affected site. The attacker who successfully
    exploited the vulnerability could then perform cross-
    origin attacks on affected systems. These attacks could
    allow the attacker to read content that the attacker is
    not authorized to read, and use the victim's identity to
    take actions on the site on behalf of the victim. The
    victim needs to be authenticated for an attacker to
    compromise the victim. The security update addresses the
    vulnerability by ensuring that Office Online Server
    properly validates origins. (CVE-2020-0695)");
  # https://support.microsoft.com/en-us/help/4484254/security-update-for-office-online-server-february-11-2020
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?3313a689");
  script_set_attribute(attribute:"solution", value:
"Microsoft has released KB4484254 to address this issue.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:M/Au:N/C:P/I:P/A:N");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2020-0695");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");

  script_set_attribute(attribute:"vuln_publication_date", value:"2020/02/11");
  script_set_attribute(attribute:"patch_publication_date", value:"2020/02/11");
  script_set_attribute(attribute:"plugin_publication_date", value:"2020/02/11");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/a:microsoft:office_online_server");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Windows : Microsoft Bulletins");

  script_copyright(english:"This script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("office_installed.nasl", "microsoft_owa_installed.nbin", "microsoft_office_compatibility_pack_installed.nbin", "smb_hotfixes.nasl", "ms_bulletin_checks_possible.nasl");
  script_require_keys("SMB/MS_Bulletin_Checks/Possible");
  script_require_ports(139, 445, "Host/patch_management_checks");

  exit(0);
}

include('audit.inc');
include('smb_func.inc');
include('smb_hotfixes.inc');
include('smb_hotfixes_fcheck.inc');
include('smb_reg_query.inc');
include('misc_func.inc');
include('install_func.inc');

get_kb_item_or_exit('SMB/MS_Bulletin_Checks/Possible');

bulletin = 'MS20-02';
kbs = make_list('4484254');
if (get_kb_item('Host/patch_management_checks')) hotfix_check_3rd_party(bulletin:bulletin, kbs:kbs, severity:SECURITY_WARNING);

get_kb_item_or_exit('SMB/Registry/Enumerated', exit_code:1);

port = kb_smb_transport();

# Get installs of Office Web Apps
owa_installs = get_installs(app_name:'Microsoft Office Web Apps');

if (!empty_or_null(owa_installs))
{
  foreach owa_install (owa_installs[1])
  {
    if (owa_install['Product'] == '2016')
    {
      oos_path = owa_install['path'];
      oos_sp = owa_install['SP'];
    }
  }
}
vuln = FALSE;

####################################################################
# Office Online Server
####################################################################
if (oos_path && (!isnull(oos_sp) && oos_sp == '0'))
{
  path = hotfix_append_path(path:oos_path, value:"ExcelServicesEcs\bin");
  if (hotfix_check_fversion(file:'xlsrv.dll', version:'16.0.10355.20000', min_version:'16.0.0.0', path:path, kb:'4484254', product:'Office Online Server') == HCF_OLDER)
  vuln = TRUE;
}

if (vuln)
{
  replace_kb_item(name:'SMB/Missing/'+bulletin, value:TRUE);
  hotfix_security_warning();
  hotfix_check_fversion_end();
  exit(0);
}
else
{
  hotfix_check_fversion_end();
  audit(AUDIT_HOST_NOT, 'affected');
}