CVE Vulnerabilities

CVE-2018-1000821

Improper Restriction of XML External Entity Reference

Published: Dec 20, 2018 | Modified: Jan 08, 2019
CVSS 3.x
10
CRITICAL
Source:
NVD
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
CVSS 2.x
7.5 HIGH
AV:N/AC:L/Au:N/C:P/I:P/A:P
RedHat/V2
RedHat/V3
Ubuntu

MicroMathematics version before commit 5c05ac8 contains a XML External Entity (XXE) vulnerability in SMathStudio files that can result in Disclosure of confidential data, denial of service, SSRF, port scanning. This attack appear to be exploitable via Specially crafted SMathStudio files. This vulnerability appears to have been fixed in after commit 5c05ac8.

Weakness

The product 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
Micromathematics Micromathematics_project * 2.17.3 (excluding)

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