CVE-2021-26855

At a glance

Severity
CRITICAL 9.1
Exploitation
Known exploited (CISA KEV) · added 2021-11-03
Exploited per ENISA since 2021-11-03
EPSS
EPSS 100.00 % · percentile 100 (2026-10-27)
State
PUBLISHED
Published
Updated
Assigner
microsoft
NVD status
Analyzed

Description

Microsoft Exchange Server Remote Code Execution Vulnerability

Scores

VersionScoreVectorScored by
CVSS 3.1CRITICAL 9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:F/RL:O/RC:Cmicrosoft
CVSS 3.1CRITICAL 9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:NNVD · secure@microsoft.com (Secondary)
CVSS 3.1CRITICAL 9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HNVD · nvd@nist.gov (Secondary)
CVSS 2.0HIGH 7.5AV:N/AC:L/Au:N/C:P/I:P/A:PNVD · nvd@nist.gov (Primary)

Weaknesses (CWE)

European references

CERT-FR advisories

Affected configurations (NVD CPE)

Affected products

ProductVersions
Microsoft · Microsoft Exchange Server 2013 Cumulative Update 21affected 15.00.0 < 15.00.1395.012
Microsoft · Microsoft Exchange Server 2013 Cumulative Update 22affected 15.00.0 < 15.00.1473.006
Microsoft · Microsoft Exchange Server 2013 Cumulative Update 23affected 15.00.0 < 15.00.1497.012
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 10affected 15.01.0 < 15.01.1531.012
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 11affected 15.01.0 < 15.01.1591.018
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 12affected 15.01.0 < 15.01.1713.010
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 13affected 15.01.0 < 15.01.1779.008
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 14affected 15.01.0 < 15.01.1847.012
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 15affected 15.01.0 < 15.01.1913.012
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 16affected 15.01.0 < 15.01.1979.008
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 17affected 15.01.0 < 15.01.2044.013
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 18affected 15.01.0 < 15.01.2106.013
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 19affected 15.01.0 < 15.01.2176.009
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 8affected 15.01.0 < 15.01.1415.010
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 9affected 15.01.0 < 15.01.1466.016
Microsoft · Microsoft Exchange Server 2019affected 15.02.0 < 15.02.0221.018
Microsoft · Microsoft Exchange Server 2019 Cumulative Update 1affected 15.02.0 < 15.01.1979.006
Microsoft · Microsoft Exchange Server 2019 Cumulative Update 2affected 15.02.0 < 15.02.0397.011
Microsoft · Microsoft Exchange Server 2019 Cumulative Update 3affected 15.02.0 < 15.02.0464.015
Microsoft · Microsoft Exchange Server 2019 Cumulative Update 4affected 15.02.0 < 15.02.0659.012

References

Sources

SourceLicence
CVE List (CVEProject cvelistV5)CVE Program Terms of Use
CISA Known Exploited VulnerabilitiesCC0 1.0
EPSS (FIRST.org)FIRST — attribution requested
ENISA EUVDENISA — reproduction authorised, source acknowledged
CERT-FR (ANSSI)Licence Ouverte / Etalab 2.0
NVD (NIST) via fkie-cad/nvd-json-data-feedsPublic domain — this product uses data from the NVD API but is not endorsed or certified by the NVD