CVE-2021-26855

Known Exploited Public Exploit
Microsoft Exchange Server Remote Code Execution Vulnerability

Description

Microsoft Exchange Server Remote Code Execution Vulnerability

Category

9.1
CVSS
Severity: Critical
CVSS 3.1 •
CVSS 2.0 •
EPSS 94.29% Top 5%
KEV Since 
Vendor Advisory microsoft.com
Affected: Microsoft Microsoft Exchange Server 2016 Cumulative Update 19
Affected: Microsoft Microsoft Exchange Server 2019 Cumulative Update 8
Affected: Microsoft Microsoft Exchange Server 2019
Affected: Microsoft Microsoft Exchange Server 2013 Cumulative Update 22
Affected: Microsoft Microsoft Exchange Server 2019 Cumulative Update 2
Affected: Microsoft Microsoft Exchange Server 2016 Cumulative Update 13
Affected: Microsoft Microsoft Exchange Server 2013 Cumulative Update 23
Affected: Microsoft Microsoft Exchange Server 2019 Cumulative Update 3
Affected: Microsoft Microsoft Exchange Server 2016 Cumulative Update 14
Affected: Microsoft Microsoft Exchange Server 2019 Cumulative Update 4
Affected: Microsoft Microsoft Exchange Server 2016 Cumulative Update 15
Affected: Microsoft Microsoft Exchange Server 2019 Cumulative Update 5
Affected: Microsoft Microsoft Exchange Server 2019 Cumulative Update 6
Affected: Microsoft Microsoft Exchange Server 2016 Cumulative Update 16
Affected: Microsoft Microsoft Exchange Server 2016 Cumulative Update 17
Affected: Microsoft Microsoft Exchange Server 2019 Cumulative Update 7
Affected: Microsoft Microsoft Exchange Server 2016 Cumulative Update 18
Affected: Microsoft Microsoft Exchange Server 2013 Cumulative Update 21
Affected: Microsoft Microsoft Exchange Server 2016 Cumulative Update 12
Affected: Microsoft Microsoft Exchange Server 2016 Cumulative Update 8
Affected: Microsoft Microsoft Exchange Server 2019 Cumulative Update 1
Affected: Microsoft Microsoft Exchange Server 2016 Cumulative Update 9
Affected: Microsoft Microsoft Exchange Server 2016 Cumulative Update 10
Affected: Microsoft Microsoft Exchange Server 2016 Cumulative Update 11
Published at:
Updated at:

References

Link Tags
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26855 patch vendor advisory
http://packetstormsecurity.com/files/161846/Microsoft-Exchange-2019-SSRF-Arbitrary-File-Write.html third party advisory vdb entry exploit
http://packetstormsecurity.com/files/161938/Microsoft-Exchange-ProxyLogon-Remote-Code-Execution.html third party advisory vdb entry exploit
http://packetstormsecurity.com/files/162610/Microsoft-Exchange-2019-Unauthenticated-Email-Download.html third party advisory vdb entry exploit
http://packetstormsecurity.com/files/162736/Microsoft-Exchange-ProxyLogon-Collector.html third party advisory vdb entry exploit

Frequently Asked Questions

What is the severity of CVE-2021-26855?
CVE-2021-26855 has been scored as a critical severity vulnerability.
How to fix CVE-2021-26855?
To fix CVE-2021-26855, make sure you are using an up-to-date version of the affected component(s) by checking the vendor release notes. As for now, there are no other specific guidelines available.
Is CVE-2021-26855 being actively exploited in the wild?
It is confirmed that CVE-2021-26855 is actively exploited. Be extra cautious if you are using vulnerable components. According to its EPSS score, there is a ~94% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2021-26855?
CVE-2021-26855 affects Microsoft Microsoft Exchange Server 2016 Cumulative Update 19, Microsoft Microsoft Exchange Server 2019 Cumulative Update 8, Microsoft Microsoft Exchange Server 2019, Microsoft Microsoft Exchange Server 2013 Cumulative Update 22, Microsoft Microsoft Exchange Server 2019 Cumulative Update 2, Microsoft Microsoft Exchange Server 2016 Cumulative Update 13, Microsoft Microsoft Exchange Server 2013 Cumulative Update 23, Microsoft Microsoft Exchange Server 2019 Cumulative Update 3, Microsoft Microsoft Exchange Server 2016 Cumulative Update 14, Microsoft Microsoft Exchange Server 2019 Cumulative Update 4, Microsoft Microsoft Exchange Server 2016 Cumulative Update 15, Microsoft Microsoft Exchange Server 2019 Cumulative Update 5, Microsoft Microsoft Exchange Server 2019 Cumulative Update 6, Microsoft Microsoft Exchange Server 2016 Cumulative Update 16, Microsoft Microsoft Exchange Server 2016 Cumulative Update 17, Microsoft Microsoft Exchange Server 2019 Cumulative Update 7, Microsoft Microsoft Exchange Server 2016 Cumulative Update 18, Microsoft Microsoft Exchange Server 2013 Cumulative Update 21, Microsoft Microsoft Exchange Server 2016 Cumulative Update 12, Microsoft Microsoft Exchange Server 2016 Cumulative Update 8, Microsoft Microsoft Exchange Server 2019 Cumulative Update 1, Microsoft Microsoft Exchange Server 2016 Cumulative Update 9, Microsoft Microsoft Exchange Server 2016 Cumulative Update 10, Microsoft Microsoft Exchange Server 2016 Cumulative Update 11.
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