“Print Nightmare” is a bug in the Windows spooler service that under some circumstances can result in an attacker being able to remotely run code on a Microsoft Windows system as the local SYSTEM user. Generally this (and subsequent patches and fixes from Microsoft) has been referred to as ‘PrintNightmare’ – but also gets mentioned as CVE-2021–1675, CVE-2021–34527 and CVE-2021–34481.
You should read the advisory from Microsoft (updated with security patch information on July 6, 2021).
It is important to note that the attacker needs to be authenticated against the remote system for the attack to be possible.
Links:
https://github.com/apple/cups/issues
https://www.papercut.com/kb/Main/PrintNightmareCVE2021
https://www.reddit.com/r/macsysadmin/comments/psoig3/printnightmare_update_broke_mac_printing/
