Microsoft Windows Print Spooler Remote Code Execution
CVE-2021-34527 is a high-severity vulnerability in Windows 10 Version 1507 from Microsoft, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. The record lists version 10.0.10240.18969 as the first without the flaw, so updating Windows 10 Version 1507 to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on November 3, 2021, which means attacks have been observed in the wild, including in ransomware campaigns.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update Windows 10 Version 1507 to 10.0.10240.18969 or a later version.
- Update Windows 10 Version 1607 to 10.0.14393.4470 or a later version.
- Update Windows 10 Version 1809 to 10.0.17763.2029 or a later version.
- CISA's required action: Apply updates per vendor instructions.
- Read the advisory on msrc.microsoft.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Microsoft | Windows 10 Version 1507 | 10.0.10240.0 up to, but not including, 10.0.10240.18969 | 10.0.10240.18969 |
| Microsoft | Windows 10 Version 1607 | 10.0.14393.0 up to, but not including, 10.0.14393.4470 | 10.0.14393.4470 |
| Microsoft | Windows 10 Version 1809 | 10.0.17763.0 up to, but not including, 10.0.17763.2029; 10.0.0 up to, but not including, 10.0.17763.2029 | 10.0.17763.2029 |
| Microsoft | Windows 10 Version 20H2 | 10.0.0 up to, but not including, 10.0.19042.1083 | 10.0.19042.1083 |
| Microsoft | Windows 10 Version 21H2 | 10.0.19044.0 up to, but not including, 10.0.19044.1415 | 10.0.19044.1415 |
| Microsoft | Windows 10 Version 22H2 | 10.0.19045.0 up to, but not including, 10.0.19045.2251 | 10.0.19045.2251 |
| Microsoft | Windows 11 version 21H2 | 10.0.22000.0 up to, but not including, 10.0.22000.318 | 10.0.22000.318 |
| Microsoft | Windows 11 version 22H2 | 10.0.22621.0 up to, but not including, 10.0.22621.674 | 10.0.22621.674 |
| Microsoft | Windows 8.1 | 6.3.0 up to, but not including, 6.3.9600.20046 | 6.3.9600.20046 |
| Microsoft | Windows Server 2008 R2 Service Pack 1 | 6.1.7601.0 up to, but not including, 6.1.7601.25633 | 6.1.7601.25633 |
| Microsoft | Windows Server 2008 R2 Service Pack 1 (Server Core installation) | 6.1.7601.0 up to, but not including, 6.1.7601.25633 | 6.1.7601.25633 |
| Microsoft | Windows Server 2008 Service Pack 2 | 6.0.6003.0 up to, but not including, 6.0.6003.21138 | 6.0.6003.21138 |
| Microsoft | Windows Server 2008 Service Pack 2 (Server Core installation) | 6.0.6003.0 up to, but not including, 6.0.6003.21138 | 6.0.6003.21138 |
| Microsoft | Windows Server 2012 | 6.2.9200.0 up to, but not including, 6.2.9200.23383 | 6.2.9200.23383 |
| Microsoft | Windows Server 2012 (Server Core installation) | 6.2.9200.0 up to, but not including, 6.2.9200.23383 | 6.2.9200.23383 |
| Microsoft | Windows Server 2012 R2 | 6.3.9600.0 up to, but not including, 6.3.9600.20046 | 6.3.9600.20046 |
| Microsoft | Windows Server 2012 R2 (Server Core installation) | 6.3.9600.0 up to, but not including, 6.3.9600.20046 | 6.3.9600.20046 |
| Microsoft | Windows Server 2016 | 10.0.14393.0 up to, but not including, 10.0.14393.4470 | 10.0.14393.4470 |
| Microsoft | Windows Server 2016 (Server Core installation) | 10.0.14393.0 up to, but not including, 10.0.14393.4470 | 10.0.14393.4470 |
| Microsoft | Windows Server 2019 | 10.0.17763.0 up to, but not including, 10.0.17763.2029 | 10.0.17763.2029 |
| Microsoft | Windows Server 2019 (Server Core installation) | 10.0.17763.0 up to, but not including, 10.0.17763.2029 | 10.0.17763.2029 |
| Microsoft | Windows Server 2022 | 10.0.20348.0 up to, but not including, 10.0.20348.230 | 10.0.20348.230 |
| Microsoft | Windows Server version 20H2 | 10.0.0 up to, but not including, 10.0.19042.1083 | 10.0.19042.1083 |
| Microsoft | Windows 10 1507 | before 10.0.10240.18969 | 10.0.10240.18969 |
| Microsoft | Windows 10 1607 | before 10.0.14393.4470 | 10.0.14393.4470 |
Version data comes from the organisation that assigned the CVE; 9 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 8.8 | High | CNA (microsoft.com) |
| CVSS 3.1 | 8.8 | High | NVD |
| CVSS 2.0 | 9.0 | High | NVD |
Official 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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Third-party and government advisories
- kb.cert.org/vuls/id/383432Third Party Advisory, US Government Resource
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-34527US Government Resource
Technical write-ups (may include proof of concept)
- packetstormsecurity.com/files/167261/Print-Spooler-Remote-DLL-Injection.htmlExploit, Third Party Advisory, VDB Entry
- vicarius.io/vsociety/posts/cve-2021-34527-printnightmare-detection-scriptExploit, Third Party Advisory
- vicarius.io/vsociety/posts/cve-2021-34527-printnightmare-mitigation-scriptExploit, Third Party Advisory
Other vulnerabilities in Windows 10 Version 1507
- 7.0 High severity
- 7.8 High severity
- 7.0 High severity
- 7.7 High severity
- 7.0 High severity
Spotted an error? Tell us.