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CVE-2021-26858

Published: Mar 2, 2021Updated: Dec 18, 2025 Sources: CVE List NVD BDUNVD-CWE-noinfo
7.8HIGH
NVD MITRE
EPSS Score
89.5%
Top 0.2%
CISA KEV
Active Exploitation
Since Nov 3, 2021
Exploits
No Known Exploits
Remediation
Patch Available

Description

Microsoft Exchange Server Remote Code Execution Vulnerability

No summary for this CVE yet.

CVSS Vector Breakdown

AV:LAC:LPR:NUI:RS:UC:HI:HA:H
Exploitability
AV:LAttack Vector
Local
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:RUser Interaction
Required
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:HAvailability
High
Open in CVSS calculator →

Weaknesses

NVD-CWE-noinfo

Affected Products

Microsoft Exchange ServerMicrosoft Corp
On-prem
Operating Systems
Microsoft Exchange Server 2019Microsoft
On-premWeb App
Enterprise Software / itsm-monitoring
Microsoft Exchange Server 2013 Cumulative Update 22Microsoft
On-prem
Operating Systems / windows
Microsoft Exchange Server 2019 Cumulative Update 2Microsoft
On-prem
Operating Systems / windows
Microsoft Exchange Server 2016 Cumulative Update 13Microsoft
On-prem
Operating Systems / windows
microsoft corpcommercialUSOperating Systemsaka microsoft corporation
microsoftcommercialUSOperating Systems
and 21 more affected products View all →

Exploitability

CISA Known Exploited Vulnerability
Added to KEV:Nov 3, 2021
Remediation due:May 3, 2022
Ransomware:Known ransomware use

Required action: Apply updates per vendor instructions.

Official Patch Available
No detection template yetWe can run the check for you — a free external exposure review, no install. Check my exposure

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26858
msrc.microsoft.com
https://nvd.nist.gov/vuln/detail/CVE-2021-26858
nvd.nist.gov
https://www.cybersecurity-help.cz/vdb/SB2021030301
cybersecurity-help.cz
and 3 more references View all →

Timeline

Published
Mar 2, 2021
Added to CISA KEV
Nov 3, 2021
Last Updated
Dec 18, 2025

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