Is CVE-2021-27065 actively exploited?

Yes. KEV Intelligence tracks CVE-2021-27065 as a known exploited vulnerability. Confidence is confirmed.

What exploitation activity has KEV Intelligence observed?

KEV Intelligence has not yet recorded sensor-observed exploitation attempts for CVE-2021-27065. Our sensors continue to monitor for activity targeting this CVE.

Which versions are affected?

CVE-2021-27065 affects Microsoft Microsoft Exchange Server 2019 and 24 other products. KEV Intelligence lists 25 version rows; examples include 15.02.0 to < publication and 15.00.0 to < publication.

Yes. CVE-2021-27065 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

Vulnerability report

Exploited in the wild Confirmed confidence In CISA KEV

CVE-2021-27065

Q: What is CVE-2021-27065?

CVE-2021-27065 is an unauthenticated Microsoft Exchange Server Remote Code Execution Vulnerability.

Q: How should organizations remediate it?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Q: Is it in CISA KEV?

Yes. CVE-2021-27065 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

Microsoft Exchange Server Remote Code Execution Vulnerability

Microsoft / Microsoft Exchange Server 2019 · affected before publication

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Severity: CVSS 7.8 · High
Confidence: Confirmed
Exploit status: Exploited in the wild
EPSS: 99.9%
First observed: —
Last observed: —

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2021-27065 is an unauthenticated Microsoft Exchange Server Remote Code Execution Vulnerability.

Is it exploited?

Yes. KEV Intelligence tracks this CVE as a known exploited vulnerability. Confidence is confirmed.

Who is affected?

Microsoft / Microsoft Exchange Server 2019 affected before publication.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

Microsoft Exchange Server Remote Code Execution Vulnerability

Vendor Product Affected Status

Microsoft Microsoft Exchange Server 2019 Before publication Affected

Microsoft Microsoft Exchange Server 2013 Cumulative Update 22 Before publication Affected

Microsoft Microsoft Exchange Server 2019 Cumulative Update 2 Before publication Affected

Microsoft Microsoft Exchange Server 2016 Cumulative Update 13 Before publication Affected

Microsoft Microsoft Exchange Server 2013 Cumulative Update 23 Before publication Affected

Microsoft Microsoft Exchange Server 2019 Cumulative Update 3 Before publication Affected

Microsoft Microsoft Exchange Server 2016 Cumulative Update 14 Before publication Affected

Microsoft Microsoft Exchange Server 2019 Cumulative Update 4 Before publication Affected

Microsoft Microsoft Exchange Server 2016 Cumulative Update 15 Before publication Affected

Microsoft Microsoft Exchange Server 2019 Cumulative Update 5 Before publication Affected

Microsoft Microsoft Exchange Server 2019 Cumulative Update 6 Before publication Affected

Microsoft Microsoft Exchange Server 2016 Cumulative Update 16 Before publication Affected

Microsoft Microsoft Exchange Server 2016 Cumulative Update 17 Before publication Affected

Microsoft Microsoft Exchange Server 2019 Cumulative Update 7 Before publication Affected

Microsoft Microsoft Exchange Server 2016 Cumulative Update 18 Before publication Affected

Microsoft Microsoft Exchange Server 2016 Cumulative Update 19 Before publication Affected

Microsoft Microsoft Exchange Server 2019 Cumulative Update 8 Before publication Affected

Microsoft Microsoft Exchange Server 2013 Service Pack 1 Before publication Affected

Microsoft Microsoft Exchange Server 2013 Cumulative Update 21 Before publication Affected

Microsoft Microsoft Exchange Server 2016 Cumulative Update 12 Before publication Affected

Microsoft Microsoft Exchange Server 2016 Cumulative Update 8 Before publication Affected

Microsoft Microsoft Exchange Server 2019 Cumulative Update 1 Before publication Affected

Microsoft Microsoft Exchange Server 2016 Cumulative Update 9 Before publication Affected

Microsoft Microsoft Exchange Server 2016 Cumulative Update 10 Before publication Affected

Microsoft Microsoft Exchange Server 2016 Cumulative Update 11 Before publication Affected

Published: 02 Mar 2021
Exploitation Reported: 03 Nov 2021
Attack vector: Local
Complexity: Low
Privileges: None
User interaction: Required

CVE References

CVE Record CVE.org · CVE Record https://www.cve.org/CVERecord?id=CVE-2021-27065
portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-27065 portal.msrc.microsoft.com · CVE Record https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CV...
packetstormsecurity.com/files/161938/Microsoft-Exchange-ProxyLogon-R... packetstormsecurity.com · CVE Record http://packetstormsecurity.com/files/161938/Microsoft-Exchange-ProxyL...
packetstormsecurity.com/files/162736/Microsoft-Exchange-ProxyLogon-C... packetstormsecurity.com · CVE Record http://packetstormsecurity.com/files/162736/Microsoft-Exchange-ProxyL...

Exploitation evidence

Why KEV Intelligence marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

CISA

Recorded 03 Nov 2021

Independent exploitation attestation added to the KEV Intelligence record.

Used in malware

CISA

Recorded 03 Nov 2021

Malware families have been linked to exploitation of this CVE.

Proof of concept available

Recorded 28 Apr 2025

Public scanner or PoC coverage increases practical exploitability.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the KEV Intelligence Pro API.

Learn about Pro API access

Source	Added
CISA First	2021-11-03 00:00 UTC
Tenable Blog	2026-06-02 14:21 UTC
CVE	2026-08-12 04:21 UTC

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets: 0
User-Agents: 0

Raw values available in Pro and Enterprise.

Scanner coverage

Metasploit template detected 28 Apr 2025.

View Metasploit template

Virtual patch status

No KEV Intelligence virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

Scanner Artifacts

Scanner and exploit-framework references linked to this CVE.

Scanner	Reference	Detected
Metasploit	https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/windows/http/exchange_proxylogon_rce.rb	28 Apr 2025

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

7.8 High

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C

EPSS

99.9%

Weaknesses

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') CWE-22

Recent mention · Tenable Blog

Inside the customer environment: Where threat actors, vulnerabilities, and exposed assets intersect

Tenable Research has developed a graph-based model linking 600+ threat groups to real-world customer exposures. It reveals which vulnerabilities sit at the intersection of severity, active exploitation, and organizational risk.Key takeawaysThe "patch everything" strategy is...

Read full advisory

All CVSS Scores

CVSS v3.1 7.8 High

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C

CVSS v2.0 6.8 Medium

AV:N/AC:M/Au:N/C:P/I:P/A:P

Potential Proof of Concepts

These PoCs are unverified and could contain malware. Use at your own risk.

exchange_proxylogon_rce

metasploit · Created Unknown

Metasploit module for CVE-2021-27065

Timeline

From disclosure to observed exploitation

12 Aug 2026
KEV confirmed by CVE

Exploitation attested by an external source
02 Jun 2026
KEV confirmed by Tenable Blog

Exploitation attested by an external source
28 Apr 2025
Metasploit module available

Exploit module available
28 Apr 2025
Public PoC available

Public proof-of-concept code published
03 Nov 2021
Added to CISA KEV

Listed in the CISA Known Exploited Vulnerabilities catalog
03 Nov 2021
First public exploitation report

Exploit observed in malware
02 Mar 2021
CVE published

Vulnerability disclosed publicly
10 Feb 2021
CVE ID reserved

Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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Evidence confidence and provenance
First-party sensor telemetry
PoC and scanner references
Affected versions and enrichment
Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2021-27065

Free JSON includes basic KEV fields

{
  "cve_id": "CVE-2021-27065",
  "confidence": "Confirmed",
  "cvss_score": 7.8,
  "cvss_estimated": false,
  "epss_score": 0.99946,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}

Early warning alerts

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CVE-2021-27065

Microsoft Exchange Server Remote Code Execution Vulnerability

Tags

CVE References

Exploited in the wild

Used in malware

Proof of concept available

Known exploited vulnerability sources

Observed signals

Scanner coverage

Virtual patch status

Scanner Artifacts

Weaknesses

Inside the customer environment: Where threat actors, vulnerabilities, and exposed assets intersect

All CVSS Scores

Potential Proof of Concepts

KEV confirmed by CVE

KEV confirmed by Tenable Blog

Metasploit module available

Public PoC available

Added to CISA KEV

First public exploitation report

CVE published

CVE ID reserved

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