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CVE-2021-26855

exploited in the wild

CVSS

9.8

Reports

8

First seen

Mar 3

Last seen

Jun 26

Affected product

Microsoft Exchange Server 2013, 2016, 2019

Associated actors

StrikeShark ×2 APT41 ×1 Curious Serpens ×1 HAFNIUM ×1 Salt Typhoon ×1 SHADOW-EARTH-053 ×1 SheldIO ×1 Storm-0501 ×1 UNC4841 ×1 APT28 ×1 Void Blizzard ×1

Recent reports

SharkLoader Malware Deploys Cobalt Strike in StrikeShark Campaign

The Hacker NewsJun 26 High

StrikeShark: New SharkLoader Campaign Delivering Cobalt Strike via Exploited Applications

Kaspersky SecurelistJun 24 High

SHADOW-EARTH-053: China-Aligned Cyberespionage Campaign Against Asian Government and Defense Sectors

Trend Micro ResearchApr 30 High

2025 Cloud Threat Hunting and Defense Landscape

Recorded Future InsiktFeb 19 High

29 Most Frequently Exploited Vulnerabilities by Hackers (2020–2021): Joint Advisory

NICS TaiwanAug 13 Critical

Microsoft Exchange Server Remote Code Execution Vulnerabilities (CVE-2021-26855, CVE-2021-26857, CVE-2021-26858, CVE-2021-27065)

NICS TaiwanMar 3 Critical

Multiple Vulnerabilities in Microsoft Exchange Server (CVE-2021-26855, CVE-2021-26857, CVE-2021-26858, CVE-2021-27065)

GovCERT.HKMar 3 Critical

Rapid Response: Mass Exploitation of On-Prem Exchange Servers

Huntress BlogMar 3

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