msrc.microsoft.com Open in urlscan Pro
13.107.246.60  Public Scan

Form analysis
0 forms found in the DOM

Text Content

You need to enable JavaScript to run this app.
Microsoft
MSRC
Security Updates
Acknowledgements
Developer


Sign in to your account
Sign in

 1. MSRC
    
 2. Customer Guidance
    
 3. Security Update Guide
    
 4. Vulnerabilities
    
 5. CVE 2021 34527


Welcome to the new and improved Security Update Guide! We'd love your feedback.
Please click here to share your thoughts or email us at
msrc_eng_support@microsoft.com. Thank you!


WINDOWS PRINT SPOOLER REMOTE CODE EXECUTION VULNERABILITY

CVE-2021-34527
On this page
Security Vulnerability

Released: Jul 1, 2021 Last updated: Jul 16, 2021

Assigning CNA:

Microsoft

MITRE CVE-2021-34527

CVSS:3.0 8.8 / 8.2

Expand all
Collapse all
Metric

Value



Base score metrics(8)
Attack Vector
This metric reflects the context by which vulnerability exploitation is
possible. The Base Score increases the more remote (logically, and physically)
an attacker can be in order to exploit the vulnerable component.
Network
The vulnerable component is bound to the network stack and the set of possible
attackers extends beyond the other options listed, up to and including the
entire Internet. Such a vulnerability is often termed 'remotely exploitable' and
can be thought of as an attack being exploitable at the protocol level one or
more network hops away (e.g., across one or more routers).
Attack Complexity
This metric describes the conditions beyond the attacker’s control that must
exist in order to exploit the vulnerability. Such conditions may require the
collection of more information about the target or computational exceptions. The
assessment of this metric excludes any requirements for user interaction in
order to exploit the vulnerability. If a specific configuration is required for
an attack to succeed, the Base metrics should be scored assuming the vulnerable
component is in that configuration.
Low
Specialized access conditions or extenuating circumstances do not exist. An
attacker can expect repeatable success against the vulnerable component.
Privileges Required
This metric describes the level of privileges an attacker must possess before
successfully exploiting the vulnerability.
Low
The attacker is authorized with (i.e., requires) privileges that provide basic
user capabilities that could normally affect only settings and files owned by a
user. Alternatively, an attacker with Low privileges may have the ability to
cause an impact only to non-sensitive resources.
User Interaction
This metric captures the requirement for a user, other than the attacker, to
participate in the successful compromise the vulnerable component. This metric
determines whether the vulnerability can be exploited solely at the will of the
attacker, or whether a separate user (or user-initiated process) must
participate in some manner.
None
The vulnerable system can be exploited without any interaction from any user.
Scope
Does a successful attack impact a component other than the vulnerable component?
If so, the Base Score increases and the Confidentiality, Integrity and
Authentication metrics should be scored relative to the impacted component.
Unchanged
An exploited vulnerability can only affect resources managed by the same
security authority. In this case, the vulnerable component and the impacted
component are either the same, or both are managed by the same security
authority.
Confidentiality
This metric measures the impact to the confidentiality of the information
resources managed by a software component due to a successfully exploited
vulnerability. Confidentiality refers to limiting information access and
disclosure to only authorized users, as well as preventing access by, or
disclosure to, unauthorized ones.
High
There is total loss of confidentiality, resulting in all resources within the
impacted component being divulged to the attacker. Alternatively, access to only
some restricted information is obtained, but the disclosed information presents
a direct, serious impact.
Integrity
This metric measures the impact to integrity of a successfully exploited
vulnerability. Integrity refers to the trustworthiness and veracity of
information.
High
There is a total loss of integrity, or a complete loss of protection. For
example, the attacker is able to modify any/all files protected by the impacted
component. Alternatively, only some files can be modified, but malicious
modification would present a direct, serious consequence to the impacted
component.
Availability
This metric measures the impact to the availability of the impacted component
resulting from a successfully exploited vulnerability. It refers to the loss of
availability of the impacted component itself, such as a networked service
(e.g., web, database, email). Since availability refers to the accessibility of
information resources, attacks that consume network bandwidth, processor cycles,
or disk space all impact the availability of an impacted component.
High
There is total loss of availability, resulting in the attacker being able to
fully deny access to resources in the impacted component; this loss is either
sustained (while the attacker continues to deliver the attack) or persistent
(the condition persists even after the attack has completed). Alternatively, the
attacker has the ability to deny some availability, but the loss of availability
presents a direct, serious consequence to the impacted component (e.g., the
attacker cannot disrupt existing connections, but can prevent new connections;
the attacker can repeatedly exploit a vulnerability that, in each instance of a
successful attack, leaks a only small amount of memory, but after repeated
exploitation causes a service to become completely unavailable).


Temporal score metrics(3)
Exploit Code Maturity
This metric measures the likelihood of the vulnerability being attacked, and is
typically based on the current state of exploit techniques, exploit code
availability, or active, 'in-the-wild' exploitation.
Functional
Functional exploit code is available. The code works in most situations where
the vulnerability exists.
Remediation Level
The Remediation Level of a vulnerability is an important factor for
prioritization. The typical vulnerability is unpatched when initially published.
Workarounds or hotfixes may offer interim remediation until an official patch or
upgrade is issued. Each of these respective stages adjusts the temporal score
downwards, reflecting the decreasing urgency as remediation becomes final.
Official Fix
A complete vendor solution is available. Either the vendor has issued an
official patch, or an upgrade is available.
Report Confidence
This metric measures the degree of confidence in the existence of the
vulnerability and the credibility of the known technical details. Sometimes only
the existence of vulnerabilities are publicized, but without specific details.
For example, an impact may be recognized as undesirable, but the root cause may
not be known. The vulnerability may later be corroborated by research which
suggests where the vulnerability may lie, though the research may not be
certain. Finally, a vulnerability may be confirmed through acknowledgement by
the author or vendor of the affected technology. The urgency of a vulnerability
is higher when a vulnerability is known to exist with certainty. This metric
also suggests the level of technical knowledge available to would-be attackers.
Confirmed
Detailed reports exist, or functional reproduction is possible (functional
exploits may provide this). Source code is available to independently verify the
assertions of the research, or the author or vendor of the affected code has
confirmed the presence of the vulnerability.

Please see Common Vulnerability Scoring System for more information on the
definition of these metrics.


EXECUTIVE SUMMARY

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.


EXPLOITABILITY

The following table provides an exploitability assessment for this vulnerability
at the time of original publication.
Publicly Disclosed

Exploited

Exploitability Assessment

Yes
Yes
Exploitation Detected


WORKAROUNDS

Determine if the Print Spooler service is running

Run the following in Windows PowerShell:

Get-Service -Name Spooler

If the Print Spooler is running or if the service is not set to disabled, select
one of the following options to either disable the Print Spooler service, or to
Disable inbound remote printing through Group Policy:

Option 1 - Disable the Print Spooler service

If disabling the Print Spooler service is appropriate for your enterprise, use
the following PowerShell commands:

Stop-Service -Name Spooler -Force

Set-Service -Name Spooler -StartupType Disabled

Impact of workaround Disabling the Print Spooler service disables the ability to
print both locally and remotely.

Option 2 - Disable inbound remote printing through Group Policy

You can also configure the settings via Group Policy as follows:

Computer Configuration / Administrative Templates / Printers

Disable the “Allow Print Spooler to accept client connections:” policy to block
remote attacks.

You must restart the Print Spooler service for the group policy to take effect.

Impact of workaround This policy will block the remote attack vector by
preventing inbound remote printing operations. The system will no longer
function as a print server, but local printing to a directly attached device
will still be possible.

For more information see: Use Group Policy settings to control printers.


FAQ

If I have not yet installed the security update released Out-of-Band on July 6
and 7, 2021, then do I need to install both the Out-of-Band security update
released on July 6 and 7, 2021, and the monthly security updates released on
July 13, 2021 to be protected from PrintNightmare?

All monthly security updates are cumulative, including the monthly security
updates released on July 13, 2021. The July 13, 2021 cumulative security updates
contain all previous security fixes - including the security fix for the print
spooler vulnerability (CVE-2021-34527). Customers who have not previously
deployed the OOB fix released on July 6 and 7, 2021, can skip deploying the OOB
update and deploy the July cumulative security updates released on July 13,
2021, to be protected.

Is this the vulnerability that has been referred to publicly as PrintNightmare?

Yes, Microsoft has assigned CVE-2021-34527 to this vulnerability.

Is this vulnerability related to CVE-2021-1675?

This vulnerability is similar but distinct from the vulnerability that is
assigned CVE-2021-1675. The attack vector is different as well. CVE-2021-1675
was addressed by the security update released on June 8, 2021.

Did the June 2021 update introduce this vulnerability?

No, the vulnerability existed before the June 8, 2021 security update.

All versions of Windows are listed in the Security Updates table. Are all
versions vulnerable?

All versions of Windows are vulnerable. As of July 7, 2021, Microsoft has
released security updates for this vulnerability for all supported versions of
Windows listed in the security updates table in this CVE.

What vulnerabilities do the security updates released on and after July 6, 2021
address?

The security updates released on and after July 6, 2021 contain protections for
a remote code execution exploit in the Windows Print Spooler service known as
“PrintNightmare”, documented in CVE-2021-34527, as well as for CVE-2021-1675.

Are Domain Controllers known to be affected by the vulnerability?

Domain controllers are affected if the print spooler service is enabled.

Are client systems and member servers that are not domain controllers known to
be affected by the vulnerability?

Yes. All editions of Windows are affected.

How can I see attack activity on my network related to this vulnerability?

Security products, like Microsoft 365 Defender, offer different ways to view
relevant alerts and telemetry. Microsoft has published our recommendations for
seeing this sort of behavior at our GitHub here: Microsoft 365 Defender Hunting
Queries. Customers using other technologies can adapt this logic for use in
their environments.

How is Point and Print technology affected by this particular vulnerability?

Point and Print is not directly related to this vulnerability, but certain
configurations make systems vulnerable to exploitation.

How does Microsoft recommend implementing Point and Print restrictions to help
secure my systems?

Please see KB5005010: Restricting installation of new printer drivers after
applying the July 6, 2021 updates for complete information.

How do I assess my Point and Print security posture to determine if my Windows
system is affected by this particular configuration?

Please see KB5005010: Restricting installation of new printer drivers after
applying the July 6, 2021 updates for complete information.


ACKNOWLEDGEMENTS

 * Zhiniang Peng (@edwardzpeng) and Xuefeng Li (@lxf02942370)

Microsoft recognizes the efforts of those in the security community who help us
protect customers through coordinated vulnerability disclosure. See
Acknowledgements for more information.


SECURITY UPDATES

To determine the support lifecycle for your software, see the Microsoft Support
Lifecycle.
Updates CVSS
Edit Columns
Download

Clear
Release date

Product

Platform

Impact

Severity

Article

Download

Details

Jul 1, 2021
Windows Server 2012 R2 (Server Core installation)
-
Remote Code Execution
Critical
 * 5004954
 * 5004958

 * Monthly Rollup
 * Security Only

CVE-2021-34527
Jul 1, 2021
Windows Server 2012 R2
-
Remote Code Execution
Critical
 * 5004954
 * 5004958

 * Monthly Rollup
 * Security Only

CVE-2021-34527
Jul 1, 2021
Windows Server 2012 (Server Core installation)
-
Remote Code Execution
Critical
 * 5004956
 * 5004960

 * Monthly Rollup
 * Security Only

CVE-2021-34527
Jul 1, 2021
Windows Server 2012
-
Remote Code Execution
Critical
 * 5004956
 * 5004960

 * Monthly Rollup
 * Security Only

CVE-2021-34527
Jul 1, 2021
Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core
installation)
-
Remote Code Execution
Critical
 * 5004953
 * 5004951

 * Monthly Rollup
 * Security Only

CVE-2021-34527
Jul 1, 2021
Windows Server 2008 R2 for x64-based Systems Service Pack 1
-
Remote Code Execution
Critical
 * 5004953
 * 5004951

 * Monthly Rollup
 * Security Only

CVE-2021-34527
Jul 1, 2021
Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core
installation)
-
Remote Code Execution
Critical
 * 5004955
 * 5004959

 * Monthly Rollup
 * Security Only

CVE-2021-34527
Jul 1, 2021
Windows Server 2008 for x64-based Systems Service Pack 2
-
Remote Code Execution
Critical
 * 5004955
 * 5004959

 * Monthly Rollup
 * Security Only

CVE-2021-34527
Jul 1, 2021
Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation)
-
Remote Code Execution
Critical
 * 5004955
 * 5004959

 * Monthly Rollup
 * Security Only

CVE-2021-34527
Jul 1, 2021
Windows Server 2008 for 32-bit Systems Service Pack 2
-
Remote Code Execution
Critical
 * 5004955
 * 5004959

 * Monthly Rollup
 * Security Only

CVE-2021-34527
Jul 1, 2021
Windows RT 8.1
-
Remote Code Execution
Critical
 * 5004954

 * Monthly Rollup

CVE-2021-34527
Jul 1, 2021
Windows 8.1 for x64-based systems
-
Remote Code Execution
Critical
 * 5004954
 * 5004958

 * Monthly Rollup
 * Security Only

CVE-2021-34527
Jul 1, 2021
Windows 8.1 for 32-bit systems
-
Remote Code Execution
Critical
 * 5004954
 * 5004958

 * Monthly Rollup
 * Security Only

CVE-2021-34527
Jul 1, 2021
Windows 7 for x64-based Systems Service Pack 1
-
Remote Code Execution
Critical
 * 5004953
 * 5004951

 * Monthly Rollup
 * Security Only

CVE-2021-34527
Jul 1, 2021
Windows 7 for 32-bit Systems Service Pack 1
-
Remote Code Execution
Critical
 * 5004953
 * 5004951

 * Monthly Rollup
 * Security Only

CVE-2021-34527
Jul 1, 2021
Windows Server 2016 (Server Core installation)
-
Remote Code Execution
Critical
 * 5004948

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows Server 2016
-
Remote Code Execution
Critical
 * 5004948

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows 10 Version 1607 for x64-based Systems
-
Remote Code Execution
Critical
 * 5004948

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows 10 Version 1607 for 32-bit Systems
-
Remote Code Execution
Critical
 * 5004948

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows 10 for x64-based Systems
-
Remote Code Execution
Critical
 * 5004950

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows 10 for 32-bit Systems
-
Remote Code Execution
Critical
 * 5004950

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows Server, version 20H2 (Server Core Installation)
-
Remote Code Execution
Critical
 * 5004945

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows 10 Version 20H2 for ARM64-based Systems
-
Remote Code Execution
Critical
 * 5004945

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows 10 Version 20H2 for 32-bit Systems
-
Remote Code Execution
Critical
 * 5004945

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows 10 Version 20H2 for x64-based Systems
-
Remote Code Execution
Critical
 * 5004945

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows Server, version 2004 (Server Core installation)
-
Remote Code Execution
Critical
 * 5004945

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows 10 Version 2004 for x64-based Systems
-
Remote Code Execution
Critical
 * 5004945

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows 10 Version 2004 for ARM64-based Systems
-
Remote Code Execution
Critical
 * 5004945

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows 10 Version 2004 for 32-bit Systems
-
Remote Code Execution
Critical
 * 5004945

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows 10 Version 21H1 for 32-bit Systems
-
Remote Code Execution
Critical
 * 5004945

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows 10 Version 21H1 for ARM64-based Systems
-
Remote Code Execution
Critical
 * 5004945

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows 10 Version 21H1 for x64-based Systems
-
Remote Code Execution
Critical
 * 5004945

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows 10 Version 1909 for ARM64-based Systems
-
Remote Code Execution
Critical
 * 5004946

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows 10 Version 1909 for x64-based Systems
-
Remote Code Execution
Critical
 * 5004946

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows 10 Version 1909 for 32-bit Systems
-
Remote Code Execution
Critical
 * 5004946

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows Server 2019 (Server Core installation)
-
Remote Code Execution
Critical
 * 5004947

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows Server 2019
-
Remote Code Execution
Critical
 * 5004947

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows 10 Version 1809 for ARM64-based Systems
-
Remote Code Execution
Critical
 * 5004947

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows 10 Version 1809 for x64-based Systems
-
Remote Code Execution
Critical
 * 5004947

 * Security Update

CVE-2021-34527
Jul 1, 2021
Windows 10 Version 1809 for 32-bit Systems
-
Remote Code Execution
Critical
 * 5004947

 * Security Update

CVE-2021-34527

Loaded all 40 rows


DISCLAIMER

The information provided in the Microsoft Knowledge Base is provided "as is"
without warranty of any kind. Microsoft disclaims all warranties, either express
or implied, including the warranties of merchantability and fitness for a
particular purpose. In no event shall Microsoft Corporation or its suppliers be
liable for any damages whatsoever including direct, indirect, incidental,
consequential, loss of business profits or special damages, even if Microsoft
Corporation or its suppliers have been advised of the possibility of such
damages. Some states do not allow the exclusion or limitation of liability for
consequential or incidental damages so the foregoing limitation may not apply.


REVISIONS

Version

Revision Date

Description

3.3
Jul 16, 2021

Added an acknowledgement. This is an informational change only.

3.2
Jul 15, 2021

Added FAQ information. This is an informational change only.

3.1
Jul 8, 2021

Added information to the executive summary and the FAQ sections. This is an
informational change only.

3.0
Jul 7, 2021

CVE updated to announce that Microsoft is releasing an update for Windows 10
version 1607, Windows Server 2016, and Windows Server 2012. Other information
has been updated as well.

2.0
Jul 6, 2021

CVE updated to announce that Microsoft is releasing an update for several
versions of Window to address this vulnerability. Updates are not yet available
for Windows 10 version 1607, Windows Server 2016, or Windows Server 2012.
Security updates for these versions of Windows will be released soon. Other
information has been updated as well. This information will be updated when more
information or updates are available.

1.4
Jul 3, 2021

Updated FAQ information. This is an informational change only.

1.3
Jul 2, 2021

Updated FAQ information. This is an informational change only.

1.1
Jul 2, 2021

The information in the workaround section was updated. This an informational
change only.

1.2
Jul 2, 2021

CVE revised to update the FAQ, add a mitigation, and add the CVSS score. These
are informational changes only.

1.0
Jul 1, 2021

Information published.