CVE-2021-26858: Microsoft Exchange Server Remote Code Execution Vulnerability

Published Mar 2, 2021
·
Updated

Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution. This vulnerability is part of the ProxyLogon exploit chain.

Other sources

Microsoft Exchange Server Remote Code Execution Vulnerability

— NVD

Affected Software

49 affected componentsFixes available
Microsoft Exchange Server=2013-cumulative_update_23
Microsoft Exchange Server=2016-cumulative_update_18
Microsoft Exchange Server=2016-cumulative_update_19
Microsoft Exchange Server=2019-cumulative_update_7
Microsoft Exchange Server=2019-cumulative_update_8
Microsoft Exchange Server 2019<15.02.0221.018
15.02.0221.018
Microsoft Exchange Server=2013-cumulative_update_21
Microsoft Exchange Server=2013-cumulative_update_22
Microsoft Exchange Server=2016-cumulative_update_10
Microsoft Exchange Server=2016-cumulative_update_11
Microsoft Exchange Server=2016-cumulative_update_12
Microsoft Exchange Server=2016-cumulative_update_13
Microsoft Exchange Server=2016-cumulative_update_14
Microsoft Exchange Server=2016-cumulative_update_15
Microsoft Exchange Server=2016-cumulative_update_16
Microsoft Exchange Server=2016-cumulative_update_17
Microsoft Exchange Server=2016-cumulative_update_8
Microsoft Exchange Server=2016-cumulative_update_9
Microsoft Exchange Server=2019
Microsoft Exchange Server=2019-cumulative_update_1
Microsoft Exchange Server=2019-cumulative_update_2
Microsoft Exchange Server=2019-cumulative_update_3
Microsoft Exchange Server=2019-cumulative_update_4
Microsoft Exchange Server=2019-cumulative_update_5
Microsoft Exchange Server=2019-cumulative_update_6
Microsoft Exchange Server
Microsoft Exchange Server 2016>=15.01.1591<15.01.1591.018
15.01.1591.018
Microsoft Exchange Server 2019>=15.01.1979<15.01.1979.006
15.01.1979.006
Microsoft Exchange Server 2016>=15.01.1466<15.01.1466.016
15.01.1466.016
Microsoft Exchange Server 2016>=15.01.1415<15.01.1415.010
15.01.1415.010
Microsoft Exchange Server 2016>=15.01.1713<15.01.1713.010
15.01.1713.010
Microsoft Exchange Server 2016>=15.01.2044<15.01.2044.013
15.01.2044.013
Microsoft Exchange Server 2016>=15.01.2176<15.01.2176.009
15.01.2176.009
Microsoft Exchange Server 2016>=15.01.2106<15.01.2106.013
15.01.2106.013
Microsoft Exchange Server 2016>=15.01.1979<15.01.1979.008
15.01.1979.008
Microsoft Exchange Server 2016>=15.01.1531<15.01.1531.012
15.01.1531.012
Microsoft Exchange Server 2016>=15.01.1847<15.01.1847.012
15.01.1847.012
Microsoft Exchange Server 2019>=15.02.0529<15.02.0529.013
15.02.0529.013
Microsoft Exchange Server 2013>=15.00.1395<15.00.1395.012
15.00.1395.012
Microsoft Exchange Server 2019>=15.02.0464<15.02.0464.015
15.02.0464.015
Microsoft Exchange Server 2019>=15.02.0721<15.02.0721.013
15.02.0721.013
Microsoft Exchange Server 2019>=15.02.0792<15.02.0792.010
15.02.0792.010
Microsoft Exchange Server 2013>=15.00.1497<15.00.1497.012
15.00.1497.012
Microsoft Exchange Server 2019>=15.02.0397<15.02.0397.011
15.02.0397.011
Microsoft Exchange Server 2013>=15.00.1473<15.00.1473.006
15.00.1473.006
Microsoft Exchange Server 2016>=15.01.1779<15.01.1779.008
15.01.1779.008
Microsoft Exchange Server 2019>=15.02.0659<15.02.0659.012
15.02.0659.012
Microsoft Exchange Server 2016>=15.01.1913<15.01.1913.012
15.01.1913.012
Microsoft Exchange Server 2019>=15.02.0595<15.02.0595.008
15.02.0595.008

Remediation

Patch Available

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26858

Patch Available

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26858

Event History

Mar 2, 2021
CVE Published
via Microsoft·04:00 PM
Data Sourced
via Microsoft·04:00 PM
DescriptionSeverityWeaknessAffected Software
CVE Published
via MITRE·11:55 PM
Data Sourced
via MITRE·11:55 PM
DescriptionSeverity
Mar 3, 2021
Data Sourced
via NVD·12:15 AM
RemedyDescriptionSeverityAffected Software
Nov 3, 2021
Known Ransomware
via CISA·12:00 AM
Data Sourced
via CISA·12:00 AM
DescriptionAffected Software
Oct 7, 2024
News Published
via BleepingComputer·02:51 PM
Nov 27, 2024
News Published
via The Register·11:44 PM
May 2, 2025
News Published
via BleepingComputer·02:32 PM
Apr 30, 2026
News Published
via The Register·11:00 AM

Peer vulnerabilities

Found alongside the following vulnerabilities.

Frequently Asked Questions

1

What is CVE-2021-26858?

CVE-2021-26858 is the identifier for the Microsoft Exchange Server Remote Code Execution Vulnerability.

2

What is the severity of CVE-2021-26858?

The severity of CVE-2021-26858 is critical.

3

How does CVE-2021-26858 impact Microsoft Exchange Server?

CVE-2021-26858 allows for remote code execution in Microsoft Exchange Server.

4

How can I protect my Microsoft Exchange Server from CVE-2021-26858?

To protect your Microsoft Exchange Server from CVE-2021-26858, apply the security updates provided by Microsoft.

5

Where can I find more information about CVE-2021-26858?

You can find more information about CVE-2021-26858 at the following link: [https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-26858](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-26858)

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Resources

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