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CVE-2021-26857

Microsoft Exchange Server Remote Code Execution Vulnerability

Microsoft Exchange ServerApplications & CMS
Open in ThreatlineRecord JSON
CVSS
7.8High
ExploitationExploited in the wildAdded to KEV 3 Nov 2021. Known ransomware useCISA KEV
Exploit odds (EPSS)95.8%Chance of exploitation activity in the next 30 days, higher than 99% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in14.03.0513.000Also 15.00.1395.012, 15.00.1473.006 and 23 moreCVE List
Federal deadline3 May 2022Remediation due date for US federal agenciesCISA KEV
CISA required actionApply updates per vendor instructions. CISA KEV

What fixes it

  • 14.03.0513.000Microsoft Exchange Server 2010 Service Pack 3CVE List
  • 15.00.1395.012Microsoft Exchange Server 2013 Cumulative Update 21CVE List
  • 15.00.1473.006Microsoft Exchange Server 2013 Cumulative Update 22CVE List
  • 15.00.1497.012Microsoft Exchange Server 2013 Cumulative Update 23CVE List
  • 15.00.0847.064Microsoft Exchange Server 2013 Service Pack 1CVE List
  • 15.01.1531.012Microsoft Exchange Server 2016 Cumulative Update 10CVE List
Show all 26 fixed versions
  • 15.01.1591.018Microsoft Exchange Server 2016 Cumulative Update 11CVE List
  • 15.01.1713.010Microsoft Exchange Server 2016 Cumulative Update 12CVE List
  • 15.01.1779.008Microsoft Exchange Server 2016 Cumulative Update 13CVE List
  • 15.01.1847.012Microsoft Exchange Server 2016 Cumulative Update 14CVE List
  • 15.01.1913.012Microsoft Exchange Server 2016 Cumulative Update 15CVE List
  • 15.01.1979.008Microsoft Exchange Server 2016 Cumulative Update 16CVE List
  • 15.01.2044.013Microsoft Exchange Server 2016 Cumulative Update 17CVE List
  • 15.01.2106.013Microsoft Exchange Server 2016 Cumulative Update 18CVE List
  • 15.01.2176.009Microsoft Exchange Server 2016 Cumulative Update 19CVE List
  • 15.01.1415.010Microsoft Exchange Server 2016 Cumulative Update 8CVE List
  • 15.01.1466.016Microsoft Exchange Server 2016 Cumulative Update 9CVE List
  • 15.02.0221.018Microsoft Exchange Server 2019CVE List
  • 15.01.1979.006Microsoft Exchange Server 2019 Cumulative Update 1CVE List
  • 15.02.0397.011Microsoft Exchange Server 2019 Cumulative Update 2CVE List
  • 15.02.0464.015Microsoft Exchange Server 2019 Cumulative Update 3CVE List
  • 15.02.0659.012Microsoft Exchange Server 2019 Cumulative Update 4CVE List
  • 15.02.0595.008Microsoft Exchange Server 2019 Cumulative Update 5CVE List
  • 15.02.0529.013Microsoft Exchange Server 2019 Cumulative Update 6CVE List
  • 15.02.0721.013Microsoft Exchange Server 2019 Cumulative Update 7CVE List
  • 15.02.0792.010Microsoft Exchange Server 2019 Cumulative Update 8CVE List

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Timeline

  1. 2 Mar 2021, 23:55 UTCPublishedCVE List
  2. 3 Nov 2021Added to CISA KEVCISA KEV

Description

Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution. This vulnerability is part of the ProxyLogon exploit chain.

Text from CVE List

Affected versions 26

  • Microsoft Exchange Server 2010 Service Pack 3affected: 14.0.0.0 before 14.03.0513.000CVE List
  • Microsoft Exchange Server 2013 Cumulative Update 21affected: 15.00.0 before 15.00.1395.012CVE List
  • Microsoft Exchange Server 2013 Cumulative Update 22affected: 15.00.0 before 15.00.1473.006CVE List
  • Microsoft Exchange Server 2013 Cumulative Update 23affected: 15.00.0 before 15.00.1497.012CVE List
  • Microsoft Exchange Server 2013 Service Pack 1affected: 15.00.0 before 15.00.0847.064CVE List
  • Microsoft Exchange Server 2016 Cumulative Update 10affected: 15.01.0 before 15.01.1531.012CVE List
  • Microsoft Exchange Server 2016 Cumulative Update 11affected: 15.01.0 before 15.01.1591.018CVE List
  • Microsoft Exchange Server 2016 Cumulative Update 12affected: 15.01.0 before 15.01.1713.010CVE List
  • Microsoft Exchange Server 2016 Cumulative Update 13affected: 15.01.0 before 15.01.1779.008CVE List
  • Microsoft Exchange Server 2016 Cumulative Update 14affected: 15.01.0 before 15.01.1847.012CVE List
  • Microsoft Exchange Server 2016 Cumulative Update 15affected: 15.01.0 before 15.01.1913.012CVE List
  • Microsoft Exchange Server 2016 Cumulative Update 16affected: 15.01.0 before 15.01.1979.008CVE List
  • Microsoft Exchange Server 2016 Cumulative Update 17affected: 15.01.0 before 15.01.2044.013CVE List
  • Microsoft Exchange Server 2016 Cumulative Update 18affected: 15.01.0 before 15.01.2106.013CVE List
  • Microsoft Exchange Server 2016 Cumulative Update 19affected: 15.01.0 before 15.01.2176.009CVE List
  • Microsoft Exchange Server 2016 Cumulative Update 8affected: 15.01.0 before 15.01.1415.010CVE List
  • Microsoft Exchange Server 2016 Cumulative Update 9affected: 15.01.0 before 15.01.1466.016CVE List
  • Microsoft Exchange Server 2019affected: 15.02.0 before 15.02.0221.018CVE List
  • Microsoft Exchange Server 2019 Cumulative Update 1affected: 15.02.0 before 15.01.1979.006CVE List
  • Microsoft Exchange Server 2019 Cumulative Update 2affected: 15.02.0 before 15.02.0397.011CVE List
  • Microsoft Exchange Server 2019 Cumulative Update 3affected: 15.02.0 before 15.02.0464.015CVE List
  • Microsoft Exchange Server 2019 Cumulative Update 4affected: 15.02.0 before 15.02.0659.012CVE List
  • Microsoft Exchange Server 2019 Cumulative Update 5affected: 15.02.0 before 15.02.0595.008CVE List
  • Microsoft Exchange Server 2019 Cumulative Update 6affected: 15.02.0 before 15.02.0529.013CVE List
  • Microsoft Exchange Server 2019 Cumulative Update 7affected: 15.02.0 before 15.02.0721.013CVE List
  • Microsoft Exchange Server 2019 Cumulative Update 8affected: 15.02.0 before 15.02.0792.010CVE List

References 3