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CVE-2021-26855

exploited in the wild☆ pin

CVSS

9.8

Reports

11

First seen

Mar 3, 2021

Last seen

Aug 10, 2026

Affected product

Microsoft Exchange Server

Associated actors

StrikeShark ×3 HAFNIUM ×2 APT 41 ×1 C0XMO ×1 Curious Serpens ×1 Lazarus Group ×1 Qilin ×1 Salt Typhoon ×1 SHADOW-EARTH-053 ×1 SheldIO ×1 Storm-0501 ×1 UNC4841 ×1 Void Blizzard ×1 APT28 ×1 Xu Zewei ×1 APT36 ×1

Recent reports

Five Years, 88,000 Backdoors, and a Pair of Handcuffs: Inside the Global Manhunt That Ended in an Arrest

Huntress BlogAug 10, 2026 High

StrikeShark Campaign Exploits Known Vulnerabilities to Deploy Cobalt Strike via SharkLoader

HKCERTJul 15, 2026 High

June 2026 CVE Landscape: 60 High-Impact Vulnerabilities Actively Exploited

Recorded Future InsiktJul 10, 2026 High

SharkLoader Malware Deploys Cobalt Strike in StrikeShark Campaign

The Hacker NewsJun 26, 2026 High

StrikeShark: New SharkLoader Campaign Delivering Cobalt Strike via Exploited Applications

Kaspersky SecurelistJun 24, 2026 High

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

Trend Micro ResearchApr 30, 2026 High

2025 Cloud Threat Hunting and Defense Landscape

Recorded Future InsiktFeb 19, 2026 High

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

NICS TaiwanAug 13, 2021 Critical

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

NICS TaiwanMar 3, 2021 Critical

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

GovCERT.HKMar 3, 2021 Critical

Rapid Response: Mass Exploitation of On-Prem Exchange Servers

Huntress BlogMar 3, 2021

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