Microsoft .NET framework SOAP Moniker PrintClientProxy remote code execution vulnerability

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.

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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.

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Solution

Apply an update

This issue is addressed in CVE-2017-8759 | .NET Framework Remote Code Execution Vulnerability

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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]
"RtfFiles"=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.

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Vendor Information

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Microsoft Corporation Affected

Updated: September 13, 2017

Status

Affected

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

Vendor References

• <https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2017-8759&gt;

CVSS Metrics

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&gt;
• <https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2017-8759&gt;

Acknowledgements

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:	2017-09-12 Date First Published: