60
CVE-2021-34527
KEV ransomware PoC ×3massPrintNightmare: Remote Code Execution in Microsoft Windows Print Spooler
CISA: Microsoft Windows Print Spooler Remote Code Execution Vulnerability
CVSS 3.1
8.8 high
EPSS
100%p100
Published
()
KEV added
AI analysis
CVE-2021-34527, widely known as 'PrintNightmare', is a remote code execution flaw in the Microsoft Windows Print Spooler service, which improperly performs privileged file operations such as loading printer driver DLLs. An attacker with low-level access who can reach a machine's spooler, for example a domain user able to add a printer connection via Point and Print, can induce the SYSTEM-privileged service to load an attacker-controlled DLL with no user interaction required (CVSS:3.1 vector AV:N/AC:L/PR:L/UI:N). Successful exploitation yields arbitrary code execution as SYSTEM, letting the attacker install programs, view, change or delete data, and create new accounts with full user rights, effectively achieving complete host compromise. The flaw affects all supported Windows client and server releases in the CISA data, Windows 10 from 1507 through 22H2, Windows 11, Windows RT 8.1, and Windows Server 2008, 2012 and 2016, wherever the Print Spooler service is running. Exploitation is confirmed in the wild: the bug was added to CISA's Known Exploited Vulnerabilities catalog on 2021-11-03 with known ransomware use, the FBI and CISA have warned of Russian actors exploiting it, and EPSS places the 30-day exploitation probability at 99.8%.
What to do: Install the July 2021 security updates immediately, released July 6, 2021 with additional updates on July 7 for Windows Server 2012, Windows Server 2016 and Windows 10 version 1607, and review KB5005010 for restricting installation of new printer drivers after applying the July 6 updates. Where patching is delayed, disable the Print Spooler service on hosts that do not need printing or restrict Point and Print, and verify that NoWarningNoElevationOnInstall and UpdatePromptSettings under HKLM\SOFTWARE\Policies\Microsoft\Windows NT\Printers\PointAndPrint are set to 0 or not defined (these keys do not exist by default, which is the secure state; NoWarningNoElevationOnInstall = 1 makes the system vulnerable by design). Prioritize domain controllers and servers with exposed spoolers, and hunt…
Affected
| microsoft Windows 10 | 1507, 1607, 1809, 20H2, 21H2, 22H2 |
| microsoft Windows 11 | 21H2, 22H2 |
| microsoft Windows RT 8.1 | 8.1 |
| microsoft Windows Server 2008 | all supported editions (source data lists no specific build range) |
| microsoft Windows Server 2012 | all supported editions (source data lists no specific build range) |
| microsoft Windows Server 2016 | all supported editions (source data lists no specific build range) |
Estimated exposure
masshundreds of millions of Windows systems (order of magnitude 10^8) — The Print Spooler service runs by default on essentially every Windows client and server installation, the advisory covers every supported Windows version, and the global Windows installed base exceeds one billion devices, implying a…
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
Description
A remote code execution vulnerability exists when the Windows Print Spooler service improperly performs privileged file operations. An attacker who successfully exploited this vulnerability could run arbitrary code with SYSTEM privileges. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. UPDATE July 7, 2021: The security update for Windows Server 2012, Windows Server 2016 and Windows 10, Version 1607 have been released. Please see the Security Updates table for the applicable update for your system. We recommend that you install these updates immediately. If you are unable to install these updates, see the FAQ and Workaround sections in this CVE for information on how to help protect your system from this vulnerability. In addition to installing the updates, in order to secure your system, you must confirm that the following registry settings are set to 0 (zero) or are not defined (Note: These registry keys do not exist by default, and therefore are already at the secure setting.), also that your Group Policy setting are correct (see FAQ): HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Printers\PointAndPrint NoWarningNoElevationOnInstall = 0 (DWORD) or not defined (default setting) UpdatePromptSettings = 0 (DWORD) or not defined (default setting) Having NoWarningNoElevationOnInstall set to 1 makes your system vulnerable by design. UPDATE July 6, 2021: Microsoft has completed the investigation and has released security updates to address this vulnerability. Please see the Security Updates table for the applicable update for your system. We recommend that you install these updates immediately. If you are unable to install these updates, see the FAQ and Workaround sections in this CVE for information on how to help protect your system from this vulnerability. See also KB5005010: Restricting installation of new printer drivers after applying the July 6, 2021 updates. Note that the security updates released on and after July 6, 2021 contain protections for CVE-2021-1675 and the additional remote code execution exploit in the Windows Print Spooler service known as “PrintNightmare”, documented in CVE-2021-34527.
CISA Known Exploited Vulnerability
- Affected
- Microsoft Windows
- Required action
- Apply updates per vendor instructions.
- Due date
- Ransomware use
- Known
- Vendors
- microsoft
- Products
- windows 10 1507, windows 10 1607, windows 10 1809, windows 10 20h2, windows 10 21h2, windows 10 22h2, windows 11 21h2, windows 11 22h2, windows rt 8.1, windows server 2008, windows server 2012, windows server 2016
- Vector
- CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
In the news20 stories
60
60
60
60
60
Windows vulnerability reported by the NSA exploited to install Russian malware
60
60
60
60
60
60
60
60
60
60
60
60
60
60