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DETECTION OVERVIEW

Windows TCP/IP Stack Exploit Attempt - CVE-2020-16899

Risk Factors

This vulnerability is well known, but vulnerable Windows devices might not be exposed to the internet or have IPv6 enabled. Because working exploit code is not publicly available, an attacker must write and test their own exploit code. A successful exploit can create a denial of service (DoS) on Windows 10 and Windows Server 2019.

Kill Chain

Exploitation

Risk Score

71

Detection diagram
Next in Exploitation: WordPress Brute Force

Attack Background

The Neighbor Discovery Protocol (NDP) facilitates host-router discovery and DNS configuration for IPv6 addresses. NDP defines ICMPv6 message types, which helps to identify relationships between devices in an IPv6 network. One of these message types is a Router Advertisement (message type 134), which can include one or more DNS Search List (DNSSL) options (option type 31). This option provides a list of DNS name suffixes that IPv6 hosts can reference when performing DNS query searches for short, unqualified domain names. The Windows TCP/IP stack has a vulnerability in how it processes the domain names found in the DNSSL option of the ICMPv6 Router Advertisement packets. An attacker creates a malicious packet with a value larger than the specified size in the Length field of the DNSSL option. The attacker sends the malicious packet to the vulnerable Windows device. The large value causes the Windows TCP/IP stack to overrun the allocated buffer size when processing the packet data. The result is a buffer overflow that can lead to a denial of service (DoS).

Mitigation Options

Install relevant patches for affected devices

If unable to patch, disable the ICMPv6 Recursive DNS Server (RDNSS) option on Windows 10 and Windows Server version 1709 and later

MITRE ATT&CK ID

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