CVE-2021-26857 HIGH

CVE-2021-26857: Microsoft Exchange Server Remote Code Execution Vulnerability

Vendor Microsoft
Product Microsoft Exchange Server 2016 Cumulative Update 19
KEV Status Known Exploited
Ransomware Used in campaigns
Published March 2, 2021
Last update October 21, 2025
View on NVD All CVEs

CVSS base score

7.8/10
Attack vector Local
Attack complexity Low
Privileges required None
User interaction Required
Confidentiality High
Integrity High

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C

What the vulnerability does

01Description

Microsoft Exchange Server Remote Code Execution Vulnerability

CISA mandated remediation

02CISA Required Action

Apply updates per vendor instructions.

Key dates

03Disclosure timeline

March 2, 2021 CVE published
October 21, 2025 Record updated