CVE-2023-21762

Spoofing via undisclosed unsafe deserialization

Published Jan 10, 2023 · Updated Feb 28, 2025

Deserialization flaw in Microsoft Exchange Server allows remote authenticated users on an adjacent network to spoof trusted identities. Microsoft identifies deserialization of untrusted data but has not disclosed the receiving component or the operation that accepts it. Exploitation requires low privileges and adjacent-network access; Microsoft has not published what is spoofed or the resulting product behavior.

CVSS severity8.0
High
EPSS probability1.55%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Deserialization flaw in Microsoft Exchange Server allows remote authenticated users on an adjacent network to spoof trusted identities. Microsoft identifies deserialization of untrusted data but has not disclosed the receiving component or the operation that accepts it. Exploitation requires low privileges and adjacent-network access; Microsoft has not published what is spoofed or the resulting product behavior.

The record

CVE
CVE-2023-21762
Published
Jan 10, 2023
Updated
Feb 28, 2025
Vendor
Microsoft
Product
Microsoft Exchange Server 2019 Cumulative Update 12
Classifications
CWE-502
Attack vector
adjacent
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 10, 2023CVE publishedPublication date reported by the CVE source.
  2. Feb 28, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=15.02.0 <15.02.1118.021

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesauthenticated

What is affected?

Microsoft · Microsoft Exchange Server 2019 Cumulative Update 12version=15.02.0 <15.02.1118.021
Microsoft · Microsoft Exchange Server 2013 Cumulative Update 23version=15.00.0 <15.00.1497.045
Microsoft · Microsoft Exchange Server 2019 Cumulative Update 11version=15.02.0 <15.02.0986.037
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 23version=15.01.0 <15.01.2507.017

Published CVSS scores

8.0Microsoft CorporationCVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-502Deserialization of Untrusted Data

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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