CVE-2021-26858CISA KEVEPSS p99.8%

CVE-2021-26858Microsoft 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 7.8 ()
VectorCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
EPSS93.65% probability of exploitation · percentile 99.8% · 2026-10-04T12:00:21Z
Last modified2026-10-01

CISA KEV entry

Added to KEV: 2021-11-03

(incoming)1

TypeTargetConfidenceTier
KEVEntryMicrosoft Exchange Server Remote Code Execution Vulnerabilitykev-cve-2021-268580%live

Related by meaning· 5

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
Microsoft Exchange Server Validation Key Remote Code Execution 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.