CVE-2021-26858

Microsoft Exchange Server Remote Code Execution Vulnerability

CVSS 3.1

7.8CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS

94% chance of exploitation in the next 30 days; higher than 99% of CVEs (scores of 2026-10-25)

CISA KEV

listed 2021-11-03, due 2022-05-03, known ransomware use

Published

2021-03-03

Modified

2026-10-01

Record from

the NVD, synced 2026-10-19

Affected

• microsoft:exchange_server

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26858
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26858
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26858

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