CVE Vulnerabilities

CVE-2021-21470

Improper Restriction of XML External Entity Reference

Published: Jan 12, 2021 | Modified: Jan 14, 2021
CVSS 3.x
4.4
MEDIUM
Source:
NVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
CVSS 2.x
3.6 LOW
AV:L/AC:L/Au:N/C:N/I:P/A:P
RedHat/V2
RedHat/V3
Ubuntu

SAP EPM Add-in for Microsoft Office, version - 1010 and SAP EPM Add-in for SAP Analysis Office, version - 2.8, allows an authenticated attacker with user privileges to parse malicious XML files which could result in XXE-based attacks in applications that accept attacker-controlled XML configuration files. This occurs as logging service does not disable XML external entities when parsing configuration files and a successful exploit would result in limited impact on integrity and availability of the application.

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
Enterprise_performance_management Sap 1010 1010
Enterprise_performance_management Sap 2.8 2.8

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