Vulnerability · CVE-2023-21529
Microsoft Exchange Server Deserialization of Untrusted Data Vulnerability
Published Feb 14, 2023 · catalog updated Aug 19, 2026 · Microsoft Exchange Server
Patch now
CVE-2023-21529 is in the CISA known-exploited catalog, due Apr 27, 2026. Confirm Microsoft Exchange Server against the vendor advisory and apply that fix. The CVSS score does not change the priority.
Gaps on this record
- No version range is stored. A customer cannot check an installed version against this record.
- Severity
- High8.8
- Known exploitation
- CISA KEV and VulnCheck KEV
- EPSS
- 59.29%
- Remediation
- Remediation guidance
- Affected products
- cpe microsoft/exchange server · vendor Microsoft Exchange Server
Microsoft Exchange Server contains a deserialization of untrusted data that allows an authenticated attacker to achieve remote code execution.
Are you affected?
Enter the version you run. The result uses only the ranges stored on this record.
The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.
- cpe microsoft/exchange server2013
- cpe microsoft/exchange server2016
- cpe microsoft/exchange server2019
- vendor Microsoft Exchange Serverversion unspecified
How to fix CVE-2023-21529
Recommended remediation
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. CISA due date Apr 27, 2026.
Official advisories
What to do
Three questions, each answered from this record only. Confirm the vendor advisory before you patch.
Should you patch?
CVE-2023-21529 is in the CISA known-exploited catalog, due Apr 27, 2026. Confirm Microsoft Exchange Server against the vendor advisory and apply that fix. The CVSS score does not change the priority.
Which versions are affected?
Compare what you have installed with microsoft/exchange server 2013; microsoft/exchange server 2016; microsoft/exchange server 2019. Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
What should an analyst verify?
CWE-502: Deserialization of Untrusted Data. EPSS 59.29%. The CISA KEV listing is the exploitation evidence. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.
Code
The project this record applies to. Exploit listings stay in References.
No public source repository is identified for this product.
Timeline
Detection, updates, and resolution for this record.
Feb 14, 2023 · Catalog
Detected
Microsoft Exchange Server contains a deserialization of untrusted data that allows an authenticated attacker to achieve remote code execution.
Apr 13, 2026 · CISA KEV
Known exploited
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Apr 27, 2026 · CISA KEV
Remediation due
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Aug 19, 2026 · Catalog
Updated
Microsoft Exchange Server contains a deserialization of untrusted data that allows an authenticated attacker to achieve remote code execution.
Sources
- CISA KEVConfirmed exploitationCVE-2023-21529
Microsoft Exchange Server contains a deserialization of untrusted data that allows an authenticated attacker to achieve remote code execution.
cisa.gov - CVE.orgVulnerability recordCVE-2023-21529
Official CVE identifier
cve.org - FIRST EPSSExploitation probabilityCVE-2023-21529
30-day exploitation probability 59.3%
first.org - NIST NVDVulnerability recordCVE-2023-21529
Microsoft Exchange Server Remote Code Execution Vulnerability
nvd.nist.gov - VulnCheck KEVConfirmed exploitationCVE-2023-21529
Microsoft Exchange Server contains a deserialization of untrusted data that allows an authenticated attacker to achieve remote code execution.
vulncheck.com
References
Freshness
Last verified in this catalog Oct 17, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.