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CVE-2021-27065

98
FAUCET Score

CVE-2021-27065 is a critical Remote Code Execution (RCE) vulnerability affecting Microsoft Exchange Server, enabling attackers to execute arbitrary code on vulnerable systems. With a CVSS score of 7.8 (HIGH), it presents a significant risk due to its low attack complexity and potential for complete compromise of confidentiality, integrity, and availability. This vulnerability is actively exploited in the wild, notably by ransomware campaigns, and has readily available exploit modules in tools like Metasploit. Its high EPSS score, FAUCET Risk Score of 100/100, and extensive community discussion and media coverage underscore its widespread impact and urgent need for remediation.

Impacted Technologies

VendorProductVersion(s)CPE
2013CPE matchmatch criteria
cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_21:*:*:*:*:*:*
2013CPE matchmatch criteria
cpe:2.3:a:microsoft:exchange_server:2013:sp1:*:*:*:*:*:*
2016CPE matchmatch criteria
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_10:*:*:*:*:*:*
2016CPE matchmatch criteria
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_11:*:*:*:*:*:*
2016CPE matchmatch criteria
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_12:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.8HIGH

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

Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
1.8
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
99.95%
Probability of exploitation in next 30 days
EPSS Percentile
100.0%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
Added to KEV · Nov 3, 2021
Metasploit: Microsoft Exchange ProxyLogon RCE · Mar 2, 2021
ExploitDB: EDB-49637 · Mar 11, 2021
This CVE's current EPSS score of 0.9995 is in the 100th percentile among its peer group of 11,621 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.2 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (26)

microsoftpatch availablevia nvd_reference
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2019
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2013 Cumulative Update 22
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2019 Cumulative Update 2
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2016 Cumulative Update 13
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2013 Cumulative Update 23
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2019 Cumulative Update 3
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2016 Cumulative Update 14
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2019 Cumulative Update 4
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2016 Cumulative Update 15
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2019 Cumulative Update 5
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2019 Cumulative Update 6
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2016 Cumulative Update 16
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2016 Cumulative Update 17
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2019 Cumulative Update 7
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2016 Cumulative Update 18
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2016 Cumulative Update 19
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2019 Cumulative Update 8
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2013 Service Pack 1
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2013 Cumulative Update 21
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2016 Cumulative Update 12
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2016 Cumulative Update 8
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2019 Cumulative Update 1
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2016 Cumulative Update 9
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2016 Cumulative Update 10
View patch
microsoftpatch availablevia msrc
Product: Microsoft Exchange Server 2016 Cumulative Update 11
View patch

Vendor Advisories (1)

microsoft2021-Mar/CVE-2021-27065Critical

Microsoft Exchange Server Remote Code Execution Vulnerability

Mar 9, 2021

References

cisa.gov / known-exploited-vulnerabilities-catalog
US Government Resource
packetstormsecurity.com / files/161938/Microsoft-Exchange-ProxyLogon-Remote-Code-Execution.html
ExploitThird Party AdvisoryVDB Entry
packetstormsecurity.com / files/162736/Microsoft-Exchange-ProxyLogon-Collector.html
ExploitThird Party AdvisoryVDB Entry
portal.msrc.microsoft.com / en-US/security-guidance/advisory/CVE-2021-27065
PatchVendor Advisory