CVE-2021-27065

mediumpriority · act · 90OT risk · criticalKEV · exploitedEPSS 0.999 · 100 %ileexploit · weaponizedEURUUS

grimoire priorityP0 · Act now

Exploitable?

Yes · in the wild

CISA KEV · 3 exploits · weaponized

Likely / severe?

99.9% (100th) EPSS

CVSS 6.8 · medium

Is it mine?

103 products

Check your exposure

Who says so?

4 sources

cnnvd · enisa_euvd · fstec_bdu · msrc_csaf

added 2021-11-03remediate by 2022-05-03

required action Apply updates per vendor instructions.

EPSS · scored 2026-10-27

Microsoft Exchange Server Remote Code Execution Vulnerability

remediations

Vendor fix, mitigation, or workaround guidance, as published by each source.

A vendor fix is available.

FixedMicrosoft Exchange Server 2013 Cumulative Update 21msrc_csaf
15.00.1395.012:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2013 Cumulative Update 22msrc_csaf
15.00.1473.006:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2013 Cumulative Update 23msrc_csaf
15.00.1497.012:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2013 Service Pack 1msrc_csaf
15.00.0847.064:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2016 Cumulative Update 10msrc_csaf
15.01.1531.012:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2016 Cumulative Update 11msrc_csaf
15.01.1591.018:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2016 Cumulative Update 12msrc_csaf
15.01.1713.010:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2016 Cumulative Update 13msrc_csaf
15.01.1779.008:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2016 Cumulative Update 14msrc_csaf
15.01.1847.012:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2016 Cumulative Update 15msrc_csaf
15.01.1913.012:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2016 Cumulative Update 16msrc_csaf
15.01.1979.008:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2016 Cumulative Update 17msrc_csaf
15.01.2044.013:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2016 Cumulative Update 18msrc_csaf
15.01.2106.013:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2016 Cumulative Update 19msrc_csaf
15.01.2176.009:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2016 Cumulative Update 8msrc_csaf
15.01.1415.010:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2016 Cumulative Update 9msrc_csaf
15.01.1466.016:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2019msrc_csaf
15.02.0221.018:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2019 Cumulative Update 1msrc_csaf
15.01.1979.006:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2019 Cumulative Update 2msrc_csaf
15.02.0397.011:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2019 Cumulative Update 3msrc_csaf
15.02.0464.015:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2019 Cumulative Update 4msrc_csaf
15.02.0659.012:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2019 Cumulative Update 5msrc_csaf
15.02.0595.008:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2019 Cumulative Update 6msrc_csaf
15.02.0529.013:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2019 Cumulative Update 7msrc_csaf
15.02.0721.013:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871
FixedMicrosoft Exchange Server 2019 Cumulative Update 8msrc_csaf
15.02.0792.010:Security Update:https://support.microsoft.com/help/5000871
https://support.microsoft.com/help/5000871

cvss

Technical severity, 0–10. One row per scoring source.

8.8

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 6.8–8.8

v2.06.8mediumAV:N/AC:M/Au:N/C:P/I:P/A:Pprimary · NVD / NIST USexploitability 8.6 · impact 6.4

v2.06.8mediumAV:N/AC:M/Au:N/C:P/I:P/A:P/E:Hsecondary · CVSS-BT (t0sche)

v3.18.8highAV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:Hsecondary · FSTEC (BDU) RU

v3.17.8highCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:Hsecondary · secure@microsoft.com USexploitability 1.8 · impact 5.9

v3.17.8highCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:Csecondary · Microsoft Security Response Center US

v3.17.8highCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:Csecondary · ENISA EU

v3.17.8highCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:Hsecondary · NVD / NIST USexploitability 1.8 · impact 5.9

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Exploitation: active · Automatable: yes · Technical Impact: totalcoordinatorcisa_ssvcUS

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-22USprimaryCWE-20US

ATT&CK techniques

ATT&CK techniques this enables or maps to.

exploits (3)

Public proof-of-concept and weaponised exploit code.

exploit/windows/http/exchange_proxylogon_rceMicrosoft Exchange ProxyLogon RCEweaponized · metasploit
EDB-49637Microsoft Exchange 2019 - Server-Side Request Forgery (Proxylogon) (PoC)PoC · exploit_db
adamrpostjr/cve-2021-27065Quick One Line Powershell scripts to detect for webshells, possible zips, and logs.PoC · poc_in_github

affected products (103)

Products and version ranges known to be affected.

Microsoft Microsoft Exchange Server 2013 Cumulative Update 2115.00.0 → publicationenisa_euvdEU
Microsoft Microsoft Exchange Server 2013 Cumulative Update 2215.00.0 → publicationenisa_euvdEU
Microsoft Microsoft Exchange Server 2013 Cumulative Update 2315.00.0 → publicationenisa_euvdEU
Microsoft Microsoft Exchange Server 2013 Service Pack 115.00.0 → publicationenisa_euvdEU
Microsoft Microsoft Exchange Server 2016 Cumulative Update 1015.01.0 → publicationenisa_euvdEU
Microsoft Microsoft Exchange Server 2016 Cumulative Update 1115.01.0 → publicationenisa_euvdEU
Microsoft Microsoft Exchange Server 2016 Cumulative Update 1215.01.0 → publicationenisa_euvdEU
Microsoft Microsoft Exchange Server 2016 Cumulative Update 1315.01.0 → publicationenisa_euvdEU
Microsoft Microsoft Exchange Server 2016 Cumulative Update 1415.01.0 → publicationenisa_euvdEU
Microsoft Microsoft Exchange Server 2016 Cumulative Update 1515.01.0 → publicationenisa_euvdEU
Microsoft Microsoft Exchange Server 2016 Cumulative Update 1615.01.0 → publicationenisa_euvdEU
Microsoft Microsoft Exchange Server 2016 Cumulative Update 1715.01.0 → publicationenisa_euvdEU
Microsoft Microsoft Exchange Server 2016 Cumulative Update 1815.01.0 → publicationenisa_euvdEU
Microsoft Microsoft Exchange Server 2016 Cumulative Update 1915.01.0 → publicationenisa_euvdEU
Microsoft Microsoft Exchange Server 2016 Cumulative Update 815.01.0 → publicationenisa_euvdEU
Microsoft Microsoft Exchange Server 2016 Cumulative Update 915.01.0 → publicationenisa_euvdEU
Microsoft Microsoft Exchange Server 201915.02.0 → publicationenisa_euvdEU
Microsoft Microsoft Exchange Server 2019 Cumulative Update 115.02.0 → publicationenisa_euvdEU
Microsoft Microsoft Exchange Server 2019 Cumulative Update 215.02.0 → publicationenisa_euvdEU
Microsoft Microsoft Exchange Server 2019 Cumulative Update 315.02.0 → publicationenisa_euvdEU

showing 20 of 103

advisories (1)

Vendor and ecosystem advisories describing this.

msrc_CVE-2021-27065Microsoft Exchange Server Remote Code Execution Vulnerability2021-03-02csaf · msrc_csafUS
To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle

also known as (4)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd fstec_bdu msrc_csaf NVD CVE.org MITRE

published 2021-03-03modified 2026-08-19

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+12520 more

references (14)

External citations — patches, advisories, analysis.

scry

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