CVE-2021-31207

mediumpriority · act · 90OT risk · criticalKEV · exploitedEPSS 0.998 · 100 %ileexploit · weaponizedEURUUS

grimoire priorityP0 · Act now

Exploitable?

Yes · in the wild

CISA KEV · 1 exploit · weaponized

Likely / severe?

99.8% (100th) EPSS

CVSS 6.5 · medium

Is it mine?

13 products

Check your exposure

Who says so?

4 sources

cnnvd · enisa_euvd · fstec_bdu · nvd

added 2021-11-03remediate by 2021-11-17

required action Apply updates per vendor instructions.

EPSS · scored 2026-10-27

Microsoft Exchange Server Security Feature Bypass Vulnerability

cvss

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

6.6

010

base score 0–10 · higher = more severe · hover a vector to decode

v2.06.5mediumAV:N/AC:L/Au:S/C:P/I:P/A:Pprimary · NVD / NIST USexploitability 8 · impact 6.4

v2.06.5mediumAV:N/AC:L/Au:S/C:P/I:P/A:P/E:Hsecondary · CVSS-BT (t0sche)

v3.16.6mediumCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:Hsecondary · NVD / NIST USexploitability 0.7 · impact 5.9

v3.16.6mediumAV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:Hsecondary · FSTEC (BDU) RU

v3.16.6mediumCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:Csecondary · ENISA EU

v3.16.6mediumCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:Hsecondary · secure@microsoft.com USexploitability 0.7 · impact 5.9

ssvc

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

Exploitation: active · Automatable: no · Technical Impact: totalcoordinatorcisa_ssvcUS

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-434USprimaryCWE-254US

ATT&CK techniques

ATT&CK techniques this enables or maps to.

exploits (1)

Public proof-of-concept and weaponised exploit code.

exploit/windows/http/exchange_proxyshell_rceMicrosoft Exchange ProxyShell RCEweaponized · metasploit

affected products (13)

Products and version ranges known to be affected.

Microsoft Microsoft Exchange Server 2013 Cumulative Update 2315.00.0 → 15.00.1497.018enisa_euvdEU
Microsoft Microsoft Exchange Server 2016 Cumulative Update 1915.01.0 → 15.01.2176.014enisa_euvdEU
Microsoft Microsoft Exchange Server 2016 Cumulative Update 2015.01.0 → 15.01.2242.010enisa_euvdEU
Microsoft Microsoft Exchange Server 2019 Cumulative Update 815.02.0 → 15.02.0792.015enisa_euvdEU
Microsoft Microsoft Exchange Server 2019 Cumulative Update 915.02.0 → 15.02.0858.012enisa_euvdEU
Microsoft Corp Microsoft Exchange Server≤ 2019 Cumulative Update 9fstec_bduRU
Microsoft Corp Microsoft Exchange Server≤ 2016 Cumulative Update 20fstec_bduRU
Microsoft Corp Microsoft Exchange Server≤ 2019 Cumulative Update 8fstec_bduRU
Microsoft Corp Microsoft Exchange Server≤ 2013 Cumulative Update 23fstec_bduRU
Microsoft Corp Microsoft Exchange Server≤ 2016 Cumulative Update 19fstec_bduRU
microsoft exchange server= 2013nvdUScpe:2.3:a:microsoft:exchange_server:*:*:*:*:*:*:*:*
microsoft exchange server= 2016nvdUScpe:2.3:a:microsoft:exchange_server:*:*:*:*:*:*:*:*
microsoft exchange server= 2019nvdUScpe:2.3:a:microsoft:exchange_server:*:*:*:*:*:*:*:*

also known as (5)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd fstec_bdu nvd NVD CVE.org MITRE

published 2021-05-11modified 2026-06-17

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+5024 more

references (13)

External citations — patches, advisories, analysis.

scry

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