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Fencer Vulns
critical 9.6

CVE-2021-26427 in the critical feed json

Microsoft Exchange Server Remote Code Execution Vulnerability

published 2021-10-13 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-13232

cvss
9.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.9%
EPSS 0.9% chance of exploitation in 30 days, percentile 59%
public exploits
0
none known

Summary

Microsoft Exchange Server Remote Code Execution Vulnerability

Patch / fix

  • Microsoft Microsoft Exchange Server 2016 Cumulative Update 22 15.01.2375.012
  • Microsoft Microsoft Exchange Server 2019 Cumulative Update 11 15.02.0986.009
  • Microsoft Microsoft Exchange Server 2013 Cumulative Update 23 15.00.1497.024
  • Microsoft Microsoft Exchange Server 2016 Cumulative Update 21 15.01.2308.015
  • Microsoft Microsoft Exchange Server 2019 Cumulative Update 10 15.02.0922.014

Exploit prediction

0.89% chance of exploitation in the next 30 days, higher than 59% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 9.0 CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C
CNA 3.1 9.0 CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
CNA 3.1 9.6 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
NVD 2.0 5.8 AV:A/AC:L/Au:N/C:P/I:P/A:P

Affected products

  • Microsoft Microsoft Exchange Server 2016 Cumulative Update 22
  • Microsoft Microsoft Exchange Server 2019 Cumulative Update 11
  • Microsoft Microsoft Exchange Server 2013 Cumulative Update 23
  • Microsoft Microsoft Exchange Server 2016 Cumulative Update 21
  • Microsoft Microsoft Exchange Server 2019 Cumulative Update 10

Classification

Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.