CVE-2022-21855

Authenticated code execution via undisclosed server flaw

Published Jan 11, 2022 · Updated Jan 2, 2025

Remote code execution in Microsoft Exchange Server 2013, 2016, and 2019 allows remote authenticated users to execute arbitrary code. Microsoft has not published the affected component, the untrusted input, or the operation that mishandles it. Exploitation requires access to an adjacent network and low privileges, and successful execution crosses the vulnerable service's security boundary.

CVSS severity9.0
Critical
EPSS probability0.93%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Remote code execution in Microsoft Exchange Server 2013, 2016, and 2019 allows remote authenticated users to execute arbitrary code. Microsoft has not published the affected component, the untrusted input, or the operation that mishandles it. Exploitation requires access to an adjacent network and low privileges, and successful execution crosses the vulnerable service's security boundary.

The record

CVE
CVE-2022-21855
Published
Jan 11, 2022
Updated
Jan 2, 2025
Vendor
Microsoft
Product
Microsoft Exchange Server 2016 Cumulative Update 21
Classifications
T1210
Attack vector
adjacent
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 11, 2022CVE publishedPublication date reported by the CVE source.
  2. Jan 2, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=15.01.0 <15.01.2308.021

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesauthenticated

What is affected?

Microsoft · Microsoft Exchange Server 2016 Cumulative Update 21version=15.01.0 <15.01.2308.021
Microsoft · Microsoft Exchange Server 2013 Cumulative Update 23version=15.00.0 <15.00.1497.028
Microsoft · Microsoft Exchange Server 2019 Cumulative Update 11version=15.02.0 <15.02.0986.015
Microsoft · Microsoft Exchange Server 2019 Cumulative Update 10version=15.02.0 <15.02.0922.020
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 22version=15.0.0 <15.01.2375.018

Published CVSS scores

7.7NIST NVDAV:A/AC:L/Au:S/C:C/I:C/A:C
9.0MicrosoftCVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1210Exploitation of Remote Services

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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