Recorded 28 Oct 2026 at 05:10 UTC. This is what ChangeIntel recorded, including the title, summary, facts and links. It is not a statement of the source's current position. See the latest record.

The historical field “Public exploit code” recorded Nuclei detection-template membership. It did not establish exploit availability. The original recorded fields remain below.

CVECISA Known Exploited Vulnerabilities

Microsoft Exchange Server Remote Code Execution Vulnerability

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

What it said

CVE: CVE-2021-26855
Vendor: Microsoft
Product: Exchange Server
CISA KEV: Listed 3 Nov 2021
Known ransomware use: Yes
Federal remediation due: 3 May 2022
Public exploit code: Nuclei template listed

Recorded links

Source evidence when recorded

CISA KEV: Complete at observationRead 28 Oct 2026 at 05:08 UTC
Public detection templates (Nuclei): Complete at observationRead 28 Oct 2026 at 05:08 UTC

Coverage describes the sources at this observation. A complete read then does not establish their current position.

What changed

Detection template: Nuclei template listed
28 Oct 2026

Page history

Changes are dated when recorded; day views use the last saved version from that UTC day, and citations stay fixed.

Cite this version

Field-level log (5)

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28 Oct 2026 · 05:10:29 UTC Public exploit codeNuclei template listed
28 Oct 2026 · 05:10:29 UTC Source coverage: public-exploit-codeCurrent
28 Oct 2026 · 05:10:29 UTC Link: Nuclei templatehttps://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-26855.yaml
23 Oct 2026 · 09:33:49 UTC Source coverage: cisa-kevIncomplete → Current
23 Oct 2026 · 08:31:50 UTC Source coverage: cisa-kevCurrent → Incomplete