Vulnerability Note VU#101048
Microsoft .NET framework SOAP Moniker PrintClientProxy remote code execution vulnerability
Original Release date: 13 Sep 2017 | Last revised: 16 Sep 2017

Overview
The Microsoft .NET framework fails to properly parse WSDL content, which can allow a remote, unauthenticated attacker to execute arbitrary code on a vulnerable system.

Description
The PrintClientProxy method in the WSDL-parsing component of the Microsoft .NET framework fails to properly handle linefeed characters.
If an attacker can trigger the .NET framework to trigger a specially-crafted WSDL file, this can result in arbitrary code execution.
This vulnerability is currently being exploited in the wild, by way of an RTF file with an embedded Soap Moniker object that triggers a remote WSDL file to be retrieved and parsed. Other attack vectors may be possible.

Impact
By causing the .NET framework to parse a specially-crafted WSDL file with the SOAP Moniker, an unauthenticated remote attacker may be able to execute arbitrary code on a vulnerable system.

Current exploits achieve this by convincing a user to open a RTF document.

Solution
Apply an update

This issue is addressed in CVE-2017-8759 | .NET Framework Remote Code Execution Vulnerability
Enable Protected View for RTF documents in Microsoft Word

Exploits in the wild utilize RTF documents.

These public exploits are blocked if Protected Mode is enabled for RTF documents in Microsoft Word. Refer to File Block Settings in the Microsoft Office Trust Center.

For example, the following registry values can be used to block the opening of RTF documents in Word 2016:

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Word\Security\FileBlock]
"RtfFilesquot;=dword:00000002

For other versions of Office, the path above will need to be modified to match the version number associated with the installed version of Office.

Vendor Information (Learn More)

VendorStatusDate NotifiedDate UpdatedMicrosoft CorporationAffected-13 Sep 2017If you are a vendor and your product is affected, let
us know.

CVSS Metrics (Learn More)

Group
Score
Vector

Base
7.5
AV:N/AC:L/Au:N/C:P/I:P/A:P

Temporal
6.5
E:H/RL:OF/RC:C

Environmental
6.5
CDP:ND/TD:H/CR:ND/IR:ND/AR:ND

References

https://www.fireeye.com/blog/threat-research/2017/09/zero-day-used-to-distribute-finspy.html
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2017-8759

Credit

This issue was discovered by Genwei Jiang and Dhanesh Kizhakkinan of FireEye, Inc.
This document was written by Will Dormann.

Other Information

CVE IDs:
CVE-2017-8759

Date Public:
12 Sep 2017

Date First Published:
13 Sep 2017

Date Last Updated:
16 Sep 2017

Document Revision:
25

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