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[ERPSCAN-15-018] SAP NetWeaver 7.4 – XXE

Application: SAP NetWeaver Portal 7.4
Vendor URL: http://www.sap.com
Bugs: XML eXternal Entity
Reported: 16.04.2015
Vendor response: 17.04.2015
Date of Public Advisory: 11.08.2015
Reference: SAP Security Note 2168485
Authors: Roman Bezhan (ERPScan)

VULNERABILITY INFORMATION
Class: XML External Entity [CWE-611]
Impact: information disclosure, denial of service
Remotely Exploitable: Yes
Locally Exploitable: No
CVE Name: CVE-2015-6662
CVSS Information
CVSS Base Score: 4.9 / 10
CVSS Base Vector:

AV : Access Vector (Related exploit range) Network (N)
AC : Access Complexity (Required attack complexity) Medium (M)
Au : Authentication (Level of authentication needed to exploit) Single (S)
C : Impact to Confidentiality Partial (P)
I : Impact to Integrity None (N)
A : Impact to Availability Partial (P)

Business Risk
The attacker can read an arbitrary file on the server by sending a correct XML request with a crafted DTD to read the reply from the service.
The attacker can perform a DoS attack (for example, an XML Entity Expansion attack).
An SMB Relay attack is a type of Man-in-the-Middle attack where the attacker asks the victim to authenticate into a machine controlled by the attacker, then relays the credentials to the target. The attacker forwards the authentication information both ways and gets access.

Description
SAP XML parser validates all incoming XML requests with a user-specified DTD.

Vulnerable Packages
SAP NetWeaver 7.4
Other versions are probably affected too, but they were not checked.

SOLUTIONS AND WORKAROUNDS
To correct this vulnerability, install SAP Security note 2168485

TECHNICAL DESCRIPTION
The vulnerability affects the functionality used by an administrator to import applications. The attacker can replace ApplicationDefinition.xml file with a malicious XML code.

PoC
Vulnerable URL http://IP:50000/irj/servlet/prt/portal/prteventname/upload/prtroot/com.sap.portal.landscape.access.LSXMLParse
Malicious file

Defense

To prevent this issue as well as a plethora of other vulnerabilities that may affect your systems, ERPScan provides the following services: