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AUSCERT Security Bulletin
ASB-2021.0136.2
Windows Print Spooler Elevation of Privilege Vulnerability
13 August 2021
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AusCERT Security Bulletin Summary
---------------------------------
Product: Microsoft Print Spooler
Operating System: Windows
Impact/Access: Increased Privileges -- Existing Account
Resolution: Mitigation
CVE Names: CVE-2021-34481
Reference: ASB-2021.0123.4
Revision History: August 13 2021: Microsoft updated advisory with security update details
July 16 2021: Initial Release
OVERVIEW
Microsoft has released an out-of-band critical update to address a
Windows Print Spooler Elevation of Privilege Vulnerability.
Microsoft has assigned CVE-2021-34481 to this vulnerability. [1]
IMPACT
Microsoft has stated the following:
"An elevation of privilege 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.
An attacker must have the ability to execute code on a victim system to
exploit this vulnerability." [1]
MITIGATION
The workaround for this vulnerability is stopping and disabling
the Print Spooler service. [1]
"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 disabled,
follow these steps:
Stop and disable the Print Spooler service
If stopping and disabling the Print Spooler service is appropriate
for your environment, run the following in Windows PowerShell:
Stop-Service -Name Spooler -Force
Set-Service -Name Spooler -StartupType Disabled
Impact of workaround Stopping and disabling the Print Spooler
service disables the ability to print both locally and remotely." [1]
========UPDATE 13/08/2021=========
Microsoft updated advisory on August 10, 2021 to announce it is
releasing security updates for all affected versions of Windows
to address this vulnerability. [1]
REFERENCES
[1] Windows Print Spooler Elevation of Privilege Vulnerability
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34481
AusCERT has made every effort to ensure that the information contained
in this document is accurate. However, the decision to use the information
described is the responsibility of each user or organisation. The decision to
follow or act on information or advice contained in this security bulletin is
the responsibility of each user or organisation, and should be considered in
accordance with your organisation's site policies and procedures. AusCERT
takes no responsibility for consequences which may arise from following or
acting on information or advice contained in this security bulletin.
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Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072
Internet Email: auscert@auscert.org.au
Facsimile: (07) 3365 7031
Telephone: (07) 3365 4417 (International: +61 7 3365 4417)
AusCERT personnel answer during Queensland business hours
which are GMT+10:00 (AEST).
On call after hours for member emergencies only.
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