CVE-2021-34523

Known Exploited Public Exploit

Microsoft Exchange Server Elevation of Privilege Vulnerability

Description

Microsoft Exchange Server Elevation of Privilege Vulnerability

9.0

CVSS

Severity: Critical

CVSS 3.1 •

CVSS 2.0 •

EPSS 94.15% Top 5%

KEV Since

Vendor Advisory microsoft.com

Affected: Microsoft Microsoft Exchange Server 2013 Cumulative Update 23

Affected: Microsoft Microsoft Exchange Server 2019 Cumulative Update 9

Affected: Microsoft Microsoft Exchange Server 2016 Cumulative Update 20

Affected: Microsoft Microsoft Exchange Server 2016 Cumulative Update 19

Affected: Microsoft Microsoft Exchange Server 2019 Cumulative Update 8

References

Link	Tags
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34523	patch vendor advisory
https://www.zerodayinitiative.com/advisories/ZDI-21-822/	third party advisory vdb entry
http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html	third party advisory vdb entry exploit

Frequently Asked Questions

What is the severity of CVE-2021-34523?: CVE-2021-34523 has been scored as a critical severity vulnerability.
How to fix CVE-2021-34523?: To fix CVE-2021-34523, 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-2021-34523 being actively exploited in the wild?: It is confirmed that CVE-2021-34523 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-2021-34523?: CVE-2021-34523 affects Microsoft Microsoft Exchange Server 2013 Cumulative Update 23, Microsoft Microsoft Exchange Server 2019 Cumulative Update 9, Microsoft Microsoft Exchange Server 2016 Cumulative Update 20, Microsoft Microsoft Exchange Server 2016 Cumulative Update 19, Microsoft Microsoft Exchange Server 2019 Cumulative Update 8.

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