CVE-2021-26855CISA KEVEPSS p100.0%

CVE-2021-26855Microsoft Exchange Server Remote Code Execution Vulnerability

Microsoft / Exchange Server

Description

Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution. This vulnerability is part of the ProxyLogon exploit chain.

Scoring

CVSS 9.1 ()
VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
EPSS100.00% probability of exploitation · percentile 100.0% · 2026-09-24T12:00:20Z
Last modified2026-08-19

CISA KEV entry

Added to KEV: 2021-11-03

(incoming)1

TypeTargetConfidenceTier
KEVEntryMicrosoft Exchange Server Remote Code Execution Vulnerabilitykev-cve-2021-268550%live

Related by meaning· 4

Nearest entities by semantic similarity across the cs-graph corpus.

CVE
Microsoft Exchange Server Information Disclosure Vulnerability
CVE
Microsoft Exchange Server Privilege Escalation Vulnerability
CVE
CVE-2026-45583
CVE
Microsoft Exchange Server Security Feature Bypass Vulnerability
Sourced from NVD + CISA KEV + FIRST.org EPSS. Curated for EU compliance use cases by Adam Lundqvist, Founder at SQUR.