Vulnerabilities > CVE-2017-8758 - Cross-site Scripting vulnerability in Microsoft Exchange Server 2016

047910
CVSS 6.1 - MEDIUM
Attack vector
NETWORK
Attack complexity
LOW
Privileges required
NONE
Confidentiality impact
LOW
Integrity impact
LOW
Availability impact
NONE
network
low complexity
microsoft
CWE-79
nessus

Summary

Microsoft Exchange Server 2016 allows an elevation of privilege vulnerability when Microsoft Exchange Outlook Web Access (OWA) fails to properly handle web requests, aka "Microsoft Exchange Cross-Site Scripting Vulnerability."

Vulnerable Configurations

Part Description Count
Application
Microsoft
1

Common Attack Pattern Enumeration and Classification (CAPEC)

  • 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.
  • Embedding Scripts in Non-Script Elements
    This attack is a form of Cross-Site Scripting (XSS) where malicious scripts are embedded in elements that are not expected to host scripts such as image tags (<img>), comments in XML documents (< !-CDATA->), etc. These tags may not be subject to the same input validation, output validation, and other content filtering and checking routines, so this can create an opportunity for an attacker to tunnel through the application's elements and launch a XSS attack through other elements. As with all remote attacks, it is important to differentiate the ability to launch an attack (such as probing an internal network for unpatched servers) and the ability of the remote attacker to collect and interpret the output of said attack.
  • Embedding Scripts within Scripts
    An attack of this type exploits a programs' vulnerabilities that are brought on by allowing remote hosts to execute scripts. The attacker leverages this capability to execute scripts to execute his/her own script by embedding it within other scripts that the target software is likely to execute. The attacker must have the ability to inject script into script that is likely to be executed. If this is done, then the attacker can potentially launch a variety of probes and attacks against the web server's local environment, in many cases the so-called DMZ, back end resources the web server can communicate with, and other hosts. With the proliferation of intermediaries, such as Web App Firewalls, network devices, and even printers having JVMs and Web servers, there are many locales where an attacker can inject malicious scripts. Since this attack pattern defines scripts within scripts, there are likely privileges to execute said attack on the host. Of course, these attacks are not solely limited to the server side, client side scripts like Ajax and client side JavaScript can contain malicious scripts as well. In general all that is required is for there to be sufficient privileges to execute a script, but not protected against writing.
  • Cross-Site Scripting in Error Pages
    An attacker distributes a link (or possibly some other query structure) with a request to a third party web server that is malformed and also contains a block of exploit code in order to have the exploit become live code in the resulting error page. When the third party web server receives the crafted request and notes the error it then creates an error message that echoes the malformed message, including the exploit. Doing this converts the exploit portion of the message into to valid language elements that are executed by the viewing browser. When a victim executes the query provided by the attacker the infected error message error message is returned including the exploit code which then runs in the victim's browser. XSS can result in execution of code as well as data leakage (e.g. session cookies can be sent to the attacker). This type of attack is especially dangerous since the exploit appears to come from the third party web server, who the victim may trust and hence be more vulnerable to deception.
  • Cross-Site Scripting Using Alternate Syntax
    The attacker uses alternate forms of keywords or commands that result in the same action as the primary form but which may not be caught by filters. For example, many keywords are processed in a case insensitive manner. If the site's web filtering algorithm does not convert all tags into a consistent case before the comparison with forbidden keywords it is possible to bypass filters (e.g., incomplete black lists) by using an alternate case structure. For example, the "script" tag using the alternate forms of "Script" or "ScRiPt" may bypass filters where "script" is the only form tested. Other variants using different syntax representations are also possible as well as using pollution meta-characters or entities that are eventually ignored by the rendering engine. The attack can result in the execution of otherwise prohibited functionality.

Nessus

NASL familyWindows : Microsoft Bulletins
NASL idSMB_NT_MS17_SEP_EXCHANGE.NASL
descriptionThe Microsoft Exchange Server installed on the remote host is missing security updates. It is, therefore, affected by multiple vulnerabilities : - An elevation of privilege vulnerability exists when Microsoft Exchange Outlook Web Access (OWA) fails to properly handle web requests. An attacker who successfully exploited this vulnerability could perform script/content injection attacks and attempt to trick the user into disclosing sensitive information. To exploit the vulnerability, an attacker could send a specially crafted email message containing a malicious link to a user. Alternatively, an attacker could use a chat client to social engineer a user into clicking the malicious link. The security update addresses the vulnerability by correcting how Microsoft Exchange validates web requests. Note: In order to exploit this vulnerability, a user must click a maliciously crafted link from an attacker. (CVE-2017-8758) - An input sanitization issue exists with Microsoft Exchange that could potentially result in unintended Information Disclosure. An attacker who successfully exploited the vulnerability could identify the existence of RFC1918 addresses on the local network from a client on the Internet. An attacker could use this internal host information as part of a larger attack. To exploit the vulnerability, an attacker could include specially crafted tags in Calendar-related messages sent to an Exchange server. These specially-tagged messages could prompt the Exchange server to fetch information from internal servers. By observing telemetry from these requests, a client could discern properties of internal hosts intended to be hidden from the Internet. The update corrects the way that Exchange parses Calendar- related messages. (CVE-2017-11761)
last seen2020-06-01
modified2020-06-02
plugin id103139
published2017-09-12
reporterThis script is Copyright (C) 2017-2018 Tenable Network Security, Inc.
sourcehttps://www.tenable.com/plugins/nessus/103139
titleSecurity Updates for Exchange (September 2017)