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                         AUSCERT Security Bulletin

                               ASB-2021.0197
       Microsoft Patch Tuesday update for Microsoft Exchange Server
                             for October 2021
                              13 October 2021

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:          Microsoft Exchange Server 2013
                  Microsoft Exchange Server 2016
                  Microsoft Exchange Server 2019
Operating System: Windows
Impact/Access:    Execute Arbitrary Code/Commands -- Existing Account            
                  Increased Privileges            -- Existing Account            
                  Denial of Service               -- Remote/Unauthenticated      
                  Provide Misleading Information  -- Remote with User Interaction
Resolution:       Patch/Upgrade
CVE Names:        CVE-2021-41350 CVE-2021-41348 CVE-2021-34453
                  CVE-2021-26427  

OVERVIEW

        Microsoft has released its monthly security patch update for the
        month of October 2021.
        
        This update resolves 4 vulnerabilities across the following products:
        [1]
        
         Microsoft Exchange Server 2013 Cumulative Update 23
         Microsoft Exchange Server 2016 Cumulative Update 21
         Microsoft Exchange Server 2016 Cumulative Update 22
         Microsoft Exchange Server 2019 Cumulative Update 10
         Microsoft Exchange Server 2019 Cumulative Update 11


IMPACT

        Microsoft has given the following details regarding these vulnerabilities.
        
         Details         Impact                   Severity
         CVE-2021-26427  Remote Code Execution    Important
         CVE-2021-34453  Denial of Service        Important
         CVE-2021-41348  Elevation of Privilege   Important
         CVE-2021-41350  Spoofing                 Important


MITIGATION

        Microsoft recommends updating the software with the version made
        available on the Microsoft Update Catalogue for the following
        Knowledge Base articles. [1].
        
         KB5007011, KB5007012


REFERENCES

        [1] Microsoft Security Update Guidance
            https://portal.msrc.microsoft.com/en-us/security-guidance

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.

===========================================================================
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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