name: Windows DNS SIGRed CVE-2020-1350
id: 36dbb206-d073-11ea-87d0-0242ac130003
version: 1
date: '2020-07-28'
author: Shannon Davis, Splunk
type: batch
description: Uncover activity consistent with CVE-2020-1350, or SIGRed. Discovered
  by Checkpoint researchers, this vulnerability affects Windows 2003 to 2019, and
  is triggered by a malicious DNS response (only affects DNS over TCP). An attacker
  can use the malicious payload to cause a buffer overflow on the vulnerable system,
  leading to compromise.  The included searches in this Analytic Story are designed
  to identify the large response payload for SIG and KEY DNS records which can be
  used for the exploit.
narrative: When a client requests a DNS record for a particular domain, that request
  gets routed first through the client's locally configured DNS server, then to any
  DNS server(s) configured as forwarders, and then onto the target domain's own DNS
  server(s).  If a attacker wanted to, they could host a malicious DNS server that
  responds to the initial request with a specially crafted large response (~65KB).  This
  response would flow through to the client's local DNS server, which if not patched
  for CVE-2020-1350, would cause the buffer overflow. The detection searches in this
  Analytic Story use wire data to detect the malicious behavior. Searches for Splunk
  Stream and Zeek are included.  The Splunk Stream search correlates across stream:dns
  and stream:tcp, while the Zeek search correlates across bro:dns:json and bro:conn:json.  These
  correlations are required to pick up both the DNS record types (SIG and KEY) along
  with the payload size (>65KB).
references:
- https://research.checkpoint.com/2020/resolving-your-way-into-domain-admin-exploiting-a-17-year-old-bug-in-windows-dns-servers/
- https://support.microsoft.com/en-au/help/4569509/windows-dns-server-remote-code-execution-vulnerability
tags:
  analytic_story: Windows DNS SIGRed CVE-2020-1350
  category:
  - Adversary Tactics
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  usecase: Advanced Threat Detection
