PrintNightmare, Critical Windows Print Spooler Vulnerability

Original release date: June 30, 2021 | Last revised: July 2, 2021

(Updated July 2, 2021) For new information and mitigations, see Microsoft's updated guidance for the Print spooler vulnerability (CVE-2021-34527).

(Updated July 1, 2021) See Microsoft's new guidance for the Print spooler vulnerability (CVE-2021-34527) and apply the necessary workarounds. 

(Original post June 30, 2021) The CERT Coordination Center (CERT/CC) has released a VulNote for a critical remote code execution vulnerability in the Windows Print spooler service, noting: “while Microsoft has released an update for CVE-2021-1675, it is important to realize that this update does not address the public exploits that also identify as CVE-2021-1675.” An attacker can exploit this vulnerability—nicknamed PrintNightmare—to take control of an affected system.

CISA encourages administrators to disable the Windows Print spooler service in Domain Controllers and systems that do not print. Additionally, administrators should employ the following best practice from Microsoft’s how-to guides, published January 11, 2021: “Due to the possibility for exposure, domain controllers and Active Directory admin systems need to have the Print spooler service disabled. The recommended way to do this is using a Group Policy Object.”