CASCACascade Atlas

Evidence dossier

CVE-2021-26857

Microsoft Exchange Server Remote Code Execution Vulnerability

76.4–93.9Priority evidence range
As known Jul 19, 2026, 5:00 AM UTCgen-56ccdaf9

Normalized restatement

Microsoft Exchange Server Remote Code Execution Vulnerability

State
PUBLISHED
Published
Mar 2, 2021
Updated
Oct 21, 2025
Evidence coverage
72%
CISA KEVCatalog member

Apply updates per vendor instructions.

FIRST EPSS94.01%

2026-07-18 · v2026.06.15 · percentile 99.8%

Source stateConflict visible

Distinct CVSS assessments remain side by side; none are averaged.

Source comparison

Who said what

CISA-ADPindependent enrichment
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CISA ADP Vulnrichment

CVEderivative copy
container

CVE Program Container

microsoftoriginal assertion
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Microsoft Exchange Server Remote Code Execution Vulnerability

CISA KEVoriginal assertion
observed_exploitation

Microsoft Exchange Server Remote Code Execution Vulnerability

FIRST EPSSoriginal assertion
model_probability

Probability 0.940080000000; percentile 0.998360000000

Applicability

Cited product scope

Trace impact →
MicrosoftMicrosoft Exchange Server 2010 Service Pack 3
[{"status": "affected", "version": "14.0.0.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2013 Cumulative Update 21
[{"status": "affected", "version": "15.00.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2013 Cumulative Update 22
[{"status": "affected", "version": "15.00.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2013 Cumulative Update 23
[{"status": "affected", "version": "15.00.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2013 Service Pack 1
[{"status": "affected", "version": "15.00.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 10
[{"status": "affected", "version": "15.01.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 11
[{"status": "affected", "version": "15.01.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 12
[{"status": "affected", "version": "15.01.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 13
[{"status": "affected", "version": "15.01.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 14
[{"status": "affected", "version": "15.01.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 15
[{"status": "affected", "version": "15.01.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 16
[{"status": "affected", "version": "15.01.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 17
[{"status": "affected", "version": "15.01.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 18
[{"status": "affected", "version": "15.01.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 19
[{"status": "affected", "version": "15.01.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 8
[{"status": "affected", "version": "15.01.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 9
[{"status": "affected", "version": "15.01.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2019
[{"status": "affected", "version": "15.02.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2019 Cumulative Update 1
[{"status": "affected", "version": "15.02.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2019 Cumulative Update 2
[{"status": "affected", "version": "15.02.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2019 Cumulative Update 3
[{"status": "affected", "version": "15.02.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2019 Cumulative Update 4
[{"status": "affected", "version": "15.02.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2019 Cumulative Update 5
[{"status": "affected", "version": "15.02.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2019 Cumulative Update 6
[{"status": "affected", "version": "15.02.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2019 Cumulative Update 7
[{"status": "affected", "version": "15.02.0", "lessThan": "publication", "versionType": "custom"}]unknown
MicrosoftMicrosoft Exchange Server 2019 Cumulative Update 8
[{"status": "affected", "version": "15.02.0", "lessThan": "publication", "versionType": "custom"}]unknown
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2010:sp3:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_22:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2013:sp1:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_10:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_11:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_12:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_13:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_14:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_15:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_16:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_17:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_18:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_19:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_8:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_9:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2019:-:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_1:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_2:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_3:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_4:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_5:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_6:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_7:*:*:*:*:*:*supported
Unknown vendorUnknown product
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_8:*:*:*:*:*:*supported

Assessments

CVSS by origin

6.8
nvd@nist.govCVSS 2.0 · role PrimaryAV:N/AC:M/Au:N/C:P/I:P/A:P
7.8
nvd@nist.govCVSS 3.1 · role SecondaryCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
7.8
secure@microsoft.comCVSS 3.1 · role SecondaryCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
7.8
microsoftCVSS 3.1 · role unknownCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C

Limitations and unknowns

  • KEV membership is authoritative for the catalog, not proof of exposure in any environment.
  • EPSS is a dated model probability and not an individual-environment prediction.
  • Affected or fixed status applies only to the exact cited product and version scope; unresolved scope remains unknown.
  • NVD-carried upstream facts remain derivative and are not independent corroboration.
  • Only NVD metrics validated under the generation-bound calculator are Public Priority eligible; direct CVE record metrics remain display-only.
  • NVD CVSS source eligibility is closed: NVD-authored, exact record-source, or registered same-CVE container origin; unmapped sources remain display-only.
  • Factor D is unknown in Public Core because no accepted canonical mapping-obligation ledger is present.
  • Core replay supports the active and immediately prior generation; retrospective valid-at replay is deferred.