Is CVE-2021-26855 actively exploited?

CVE-2021-26855 has no public evidence of in-the-wild exploitation as of 2025-12-18.

What is the CVSS score for CVE-2021-26855?

CVE-2021-26855 has a CVSS score of 9.1 (CRITICAL severity). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.

How do I patch CVE-2021-26855?

Patch guidance is available from microsoft security advisories. CVEDatabase generates AI-assisted remediation guidance on demand for CVE-2021-26855.

Fix CVE-2021-26855 - CRITICAL microsoft exchange server

Q: Which products are affected by CVE-2021-26855?

24 products: microsoft exchange server, microsoft exchange server, microsoft exchange server, microsoft exchange server, microsoft exchange server, and 19 more.

Description

Microsoft Exchange Server Remote Code Execution Vulnerability

CVSS Metrics

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Attack Vector: network
Complexity: low
Privileges: none
User Action: none
Scope: unchanged
Confidentiality: high
Integrity: high
Availability: none
Weaknesses: CWE-918 · Server-Side Request Forgery CWE-918 · Server-Side Request Forgery

Metadata

Primary Vendor: MICROSOFT
Published: 3/3/2021
Last Modified: 12/18/2025
Source: NIST NVD
Note: Verify all details with official vendor sources before applying patches.

Affected Products

microsoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_servermicrosoft : exchange_server

Remediation Guidance

Executive Summary

View on NIST NVD