CVE-2021-26857

7.8 highKEVEPSS 96%

High (7.8) in Microsoft Exchange Server. In CISA KEV since 2021-11-03, with known ransomware use. EPSS 96% chance of exploitation in the next 30 days.

Microsoft Exchange Server Remote Code Execution Vulnerability

Severity

CVSS 3.1

7.8 high

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

EPSS: 96% chance of exploitation in the next 30 days; higher than 99% of CVEs (scores of 2026-10-31)
CISA KEV: listed 2021-11-03, due 2022-05-03, known ransomware use
CWE: CWE-502
Published: 2021-03-03
Modified: 2026-08-19
Record from: the NVD, synced 2026-10-19

Affected

microsoft:exchange_server

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26857
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26857
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26857

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