CVE-2020-1350 – SIGRed Windows DNS Server Remote Code Execution Vulnerability

Published: 2020-07-14
MITRE CVE-2020-1350

“A remote code execution vulnerability exists in Windows Domain Name System servers when they fail to properly handle requests. An attacker who successfully exploited the vulnerability could run arbitrary code in the context of the Local System Account. Windows servers that are configured as DNS servers are at risk from this vulnerability.”

The tricky part about this is that a lot of systems normally closed of from direct access to the internet has an indirect access to the internet via the forwarding capabilities built in to DNS. If you are able to resolve regular domains like “”, “” and “”, and you are asking your Windows Domain Controller, that Domain Controller is vulnerable.

The recommended cause of action is to upgrade as soon as possible. This requires a reboot. There exists a workaround, if a reboot is not something you can do right now. This is a registry edit and only requires a restart of the DNS Service. We refer to official documentation for information about this workaround.

In our experience, and based on information currently available, we expect to see working exploits in the wild within a week, and see it likely that there will be widespread active attacks within 2 weeks.

Basefarm is tracking this vulnerability internally as BF-VLN-2084547, with the highest priority. All internal Basefarm servers vulnerable is scheduled to receive patches within 2020-07-15 18:00. We are currently chasing customer-specific servers and organizing emergency patching.

Update 2020-07-17 21:00 – All change-tickets for customer-specific servers have attention. 4% of the tickets is still in implementation status, 96% is either in Post-implementation Review status or Closed status. We continue to monitor intelligence sources for signs of active exploitation and will ensure priority for the remaining 4% of customers.

Update 2020-07-21 – All servers are patched or have implemented workarounds for this vulnerability.

Official Microsoft Security Advisory