CVE-2021-26858
high CISA KEVMicrosoft Exchange Server Remote Code Execution Vulnerability
Vendor / product: Microsoft — Exchange Server
Microsoft Exchange Server Remote Code Execution Vulnerability
CVSS
7.8
7.8 (CVSS v3.1)
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H Severity source: NVD CVSS v3.1 (secure@microsoft.com)
Timeline (UTC)
Published: 2021-03-03 00:15
Modified: 2026-10-01 21:17
NVD status: Analyzed
Last synced 1 day ago
Verified against the source API 2026-10-27 07:07 UTC
Exploitation
Listed in CISA KEV
Added 2021-11-03 · due 2022-05-03
Known ransomware use: Known
Required action (CISA)
Apply updates per vendor instructions.
Affected products
microsoft / exchange_server 2013, 2016, 2019
Weakness classification (CWE)
NVD-CWE-noinfo
Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.
Mitigation & advisories
Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26858
Patch / mitigation: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26858
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26858 secure@microsoft.com
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26858 af854a3a-2127-422b-91ae-364da2661108
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26858 134c704f-9b21-4f2e-91b3-4a467353bcc0
Data sources
CISA KEV — fetched 2026-10-27 06:50 UTC · record ↗
NVD CVE API 2.0 — fetched 2026-10-27 07:07 UTC · record ↗