Skip to main content

Exchange Server CVE-2021-26858

HIGH
2021-03-03 secure@microsoft.com
Microsoft RCE Exchange Server
7.8
CVSS 3.1 · Vendor: microsoft
Share

Severity by source

Vendor (microsoft) PRIMARY
7.8 HIGH
AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Primary rating from Vendor (microsoft) · only source for this CVE.

CVSS VectorVendor: microsoft

Attack Vector
Local
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

4
Analysis Generated
Mar 26, 2026 - 11:19 vuln.today
Added to CISA KEV
Dec 18, 2025 - 02:00 cisa
CISA KEV
Patch released
Dec 18, 2025 - 02:00 nvd
Patch available
CVE Published
Mar 03, 2021 - 00:15 nvd
HIGH 7.8

DescriptionCVE.org

Microsoft Exchange Server Remote Code Execution Vulnerability

AnalysisAI

Microsoft Exchange Server allows authenticated attackers to write arbitrary files to the server filesystem, the third component of the ProxyLogon exploit chain enabling web shell deployment.

Technical ContextAI

The post-authentication file write vulnerability allows writing arbitrary content to any filesystem location accessible by the Exchange service account (SYSTEM). Combined with the SSRF (CVE-2021-26855) for authentication bypass, this enables unauthenticated web shell deployment.

RemediationAI

Apply security updates. Scan for web shells in Exchange web directories. Monitor file creation events in IIS content directories.

More in Exchange Server

View all
CVE-2021-34473 CRITICAL POC
9.1 Jul 14

Microsoft Exchange Server contains a pre-authentication SSRF vulnerability known as 'ProxyShell' that allows unauthentic
CVE-2021-26855 CRITICAL POC
9.1 Mar 03

Microsoft Exchange Server contains a server-side request forgery (SSRF) vulnerability known as 'ProxyLogon' that allows

CVE-2021-34523 CRITICAL POC
9.0 Jul 14

Microsoft Exchange Server contains a privilege escalation vulnerability in the PowerShell backend that allows authentica
CVE-2021-27065 HIGH POC
7.8 Mar 03

Microsoft Exchange Server allows post-authentication arbitrary file write that enables web shell deployment, the primary
CVE-2021-42321 HIGH POC
8.8 Nov 10

Microsoft Exchange Server Remote Code Execution Vulnerability. Rated high severity (CVSS 8.8), this vulnerability is rem
CVE-2021-33766 HIGH POC
7.3 Jul 14

Microsoft Exchange Server Information Disclosure Vulnerability. Rated high severity (CVSS 7.3), this vulnerability is re
CVE-2022-41080 HIGH
8.8 Nov 09

Microsoft Exchange Server Elevation of Privilege Vulnerability. Rated high severity (CVSS 8.8), this vulnerability is re
CVE-2023-21529 HIGH POC
8.8 Feb 14

Remote code execution in Microsoft Exchange Server 2013, 2016, and 2019 allows authenticated attackers to execute arbitr
CVE-2021-41349 MEDIUM POC
6.5 Nov 10

Microsoft Exchange Server Spoofing Vulnerability. Rated medium severity (CVSS 6.5), this vulnerability is remotely explo
CVE-2021-26857 HIGH
7.8 Mar 03

Microsoft Exchange Server Unified Messaging service contains a deserialization vulnerability that allows authenticated a
CVE-2021-31196 HIGH
7.2 Jul 14

Microsoft Exchange Server Remote Code Execution Vulnerability. Rated high severity (CVSS 7.2), this vulnerability is rem
CVE-2023-21707 HIGH
8.8 Feb 14

Microsoft Exchange Server Remote Code Execution Vulnerability. Rated high severity (CVSS 8.8), this vulnerability is rem

Same technique RCE

View all
CVE-2021-44228 CRITICAL POC
10.0
CVE-2017-7269 CRITICAL POC
9.8
CVE-2022-47966 CRITICAL POC
9.8
CVE-2012-4681 CRITICAL POC
9.8
CVE-2023-3519 CRITICAL POC
9.8
CVE-2015-5119 CRITICAL POC
9.8
CVE-2016-4117 CRITICAL POC
9.8
CVE-2015-3113 CRITICAL POC
9.8

Share

CVE-2021-26858 vulnerability details – vuln.today
Back

This site uses cookies essential for authentication and security. No tracking or analytics cookies are used. Privacy Policy