Live › vulnerability › CVE-2021-26855
Go to dashboardMicrosoft Exchange Server has a remote code execution flaw, part of the ProxyLogon chain, that is actively exploited in the wild and tied to ransomware use. An unauthenticated attacker who reaches the Exchange server over the network can run code on it.
Summary written from the sources below. Check the originals before acting.
First seen by InfraStack 2026-10-23 19:11 UTC, 3h before NVD. All times on this page are UTC.
Apply updates per vendor instructions.
| Product | Ecosystem | Affected | Fixed in |
|---|---|---|---|
| Microsoft Exchange Server | vendor | – | – |
Unknown from the sources. In the analyst’s queue.
Apply Microsoft's updates for CVE-2021-26855 per vendor instructions (CISA required action); the specific patched build numbers are not in the sources.
Each row is the first time that source carried this signal. The analyst’s rows are its own findings.
Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution. This vulnerability is part of the ProxyLogon exploit chain.
CISA required action: Apply updates per vendor instructions.
This page as .md · .json · in your agent: get_signal("CVE-2021-26855")
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