CVE-2021-27065

Name: CVE-2021-27065
Creator: NVD / NIST
Published: 2021-03-03T00:15:12.307+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.8/10Actively ExploitedEPSS 99.95%

Last modified Jun 17, 2026

CVE-2021-27065 is a high-severity vulnerability rated 7.8/10 on the CVSS scale. Microsoft Exchange Server Remote Code Execution Vulnerability. CISA has confirmed active exploitation in the wild. EPSS estimates a 99.95% chance of exploitation in the next 30 days.

Description

Microsoft Exchange Server Remote Code Execution Vulnerability

Metrics

CVSS 3.1

7.8/10

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS Probability

99.95%

100.0th percentile

Probability of exploitation in the next 30 days. Learn more

Exploitation Status

This vulnerability is listed in CISA’s Known Exploited Vulnerabilities catalog, confirming active exploitation in the wild. Federal agencies must remediate by May 3, 2022.

Weakness Enumeration

Affected Software

Vendor	Product	Versions	Update
Microsoft	Exchange Server	2013	Cumulative Update 21
Microsoft	Exchange Server	2016	Cumulative Update 10
Microsoft	Exchange Server	2019	—

References

http://packetstormsecurity.com/files/161938/Microsoft-Exchange-ProxyLogon-Remote-Code-Execution.htmlExploit, Third Party Advisory, VDB Entry
http://packetstormsecurity.com/files/162736/Microsoft-Exchange-ProxyLogon-Collector.htmlExploit, Third Party Advisory, VDB Entry
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-27065Patch, Vendor Advisory
http://packetstormsecurity.com/files/161938/Microsoft-Exchange-ProxyLogon-Remote-Code-Execution.htmlExploit, Third Party Advisory, VDB Entry
http://packetstormsecurity.com/files/162736/Microsoft-Exchange-ProxyLogon-Collector.htmlExploit, Third Party Advisory, VDB Entry
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-27065Patch, Vendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-27065US Government Resource

Timeline

Published: Mar 3, 2021
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2021-27065?

Microsoft Exchange Server Remote Code Execution Vulnerability

How severe is CVE-2021-27065?

CVE-2021-27065 has a CVSS score of 7.8/10 (HIGH severity). The EPSS model estimates a 99.95% probability of exploitation in the next 30 days. This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog.

How do I fix CVE-2021-27065?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-27065?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST