Exploited
critical
9.8
CWE
918
Advisory Published
Updated

CVE-2021-26855: Microsoft Exchange Server Remote Code Execution Vulnerability

First published: Tue Mar 02 2021(Updated: )

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

Credit: secure@microsoft.com secure@microsoft.com secure@microsoft.com

Affected SoftwareAffected VersionHow to fix
Microsoft Exchange Server=2013-cumulative_update_21
Microsoft Exchange Server=2013-cumulative_update_22
Microsoft Exchange Server=2013-cumulative_update_23
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_18
Microsoft Exchange Server=2016-cumulative_update_19
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=2019-cumulative_update_7
Microsoft Exchange Server=2019-cumulative_update_8
Microsoft Exchange Server
=2013-cumulative_update_21
=2013-cumulative_update_22
=2013-cumulative_update_23
=2016-cumulative_update_10
=2016-cumulative_update_11
=2016-cumulative_update_12
=2016-cumulative_update_13
=2016-cumulative_update_14
=2016-cumulative_update_15
=2016-cumulative_update_16
=2016-cumulative_update_17
=2016-cumulative_update_18
=2016-cumulative_update_19
=2016-cumulative_update_8
=2016-cumulative_update_9
=2019
=2019-cumulative_update_1
=2019-cumulative_update_2
=2019-cumulative_update_3
=2019-cumulative_update_4
=2019-cumulative_update_5
=2019-cumulative_update_6
=2019-cumulative_update_7
=2019-cumulative_update_8

Remedy

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26855

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Reference Links

Peer vulnerabilities

(Found alongside the following vulnerabilities)

Frequently Asked Questions

  • What is CVE-2021-26855?

    CVE-2021-26855 is a remote code execution vulnerability in Microsoft Exchange Server.

  • What is the severity of CVE-2021-26855?

    The severity of CVE-2021-26855 is critical, with a severity value of 9.8.

  • Which products are affected by CVE-2021-26855?

    Microsoft Exchange Server versions 2013, 2016, and 2019 are affected by CVE-2021-26855.

  • How do I fix CVE-2021-26855?

    Update your Microsoft Exchange Server to the latest cumulative update to fix CVE-2021-26855.

  • Where can I find more information about CVE-2021-26855?

    You can find more information about CVE-2021-26855 in the references provided: [CISA Emergency Directive 21-02](https://www.cisa.gov/emergency-directive-21-02), [Packet Storm Security](http://packetstormsecurity.com/files/161846/Microsoft-Exchange-2019-SSRF-Arbitrary-File-Write.html), [Packet Storm Security](http://packetstormsecurity.com/files/161938/Microsoft-Exchange-ProxyLogon-Remote-Code-Execution.html).

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