CVE Vulnerabilities

CVE-2019-0795

Improper Restriction of XML External Entity Reference

Published: Apr 09, 2019 | Modified: Apr 11, 2019
CVSS 3.x
8.8
HIGH
Source:
NVD
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CVSS 2.x
9.3 HIGH
AV:N/AC:M/Au:N/C:C/I:C/A:C
RedHat/V2
RedHat/V3
Ubuntu

A remote code execution vulnerability exists when the Microsoft XML Core Services MSXML parser processes user input, aka ‘MS XML Remote Code Execution Vulnerability’. This CVE ID is unique from CVE-2019-0790, CVE-2019-0791, CVE-2019-0792, CVE-2019-0793.

Weakness

The software processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.

Affected Software

Name Vendor Start Version End Version
Windows_10 Microsoft - -
Windows_10 Microsoft 1607 1607
Windows_10 Microsoft 1703 1703
Windows_10 Microsoft 1709 1709
Windows_10 Microsoft 1803 1803
Windows_10 Microsoft 1809 1809
Windows_7 Microsoft - -
Windows_8.1 Microsoft - -
Windows_rt_8.1 Microsoft - -
Windows_server_2008 Microsoft - -
Windows_server_2008 Microsoft r2 r2
Windows_server_2008 Microsoft r2 r2
Windows_server_2012 Microsoft - -
Windows_server_2012 Microsoft r2 r2
Windows_server_2016 Microsoft - -
Windows_server_2016 Microsoft 1709 1709
Windows_server_2016 Microsoft 1803 1803
Windows_server_2019 Microsoft - -

Extended Description

XML documents optionally contain a Document Type Definition (DTD), which, among other features, enables the definition of XML entities. It is possible to define an entity by providing a substitution string in the form of a URI. The XML parser can access the contents of this URI and embed these contents back into the XML document for further processing. By submitting an XML file that defines an external entity with a file:// URI, an attacker can cause the processing application to read the contents of a local file. For example, a URI such as “file:///c:/winnt/win.ini” designates (in Windows) the file C:\Winnt\win.ini, or file:///etc/passwd designates the password file in Unix-based systems. Using URIs with other schemes such as http://, the attacker can force the application to make outgoing requests to servers that the attacker cannot reach directly, which can be used to bypass firewall restrictions or hide the source of attacks such as port scanning. Once the content of the URI is read, it is fed back into the application that is processing the XML. This application may echo back the data (e.g. in an error message), thereby exposing the file contents.

Potential Mitigations

References