# CVE-2021-42321

Microsoft Exchange Server Remote Code Execution Vulnerability

- Page: https://www.vulneraibility.com/cve/CVE-2021-42321
- CVSS: 8.8
- Known exploited: yes, in CISA KEV since 2021-11-17; CISA due date 2021-12-01; known ransomware use
- EPSS: 91.74% (percentile 99.8)
- Public exploit code: 1 Metasploit module · 3 GitHub proofs of concept (first 2021-11-23)
- CISA SSVC: exploitation active, automatable no, technical impact total (assessed 2024-01-03)
- Published: 2021-11-10

## Affected versions

- Microsoft Microsoft Exchange Server 2016 Cumulative Update 21: affected >= 15.01.0 and < 15.01.2308.020
- Microsoft Microsoft Exchange Server 2016 Cumulative Update 22: affected >= 15.0.0 and < 15.01.2375.017
- Microsoft Microsoft Exchange Server 2019 Cumulative Update 10: affected >= 15.02.0 and < 15.02.0792.019
- Microsoft Microsoft Exchange Server 2019 Cumulative Update 11: affected >= 15.02.0 and < 15.02.0986.014

A version outside these ranges is not a statement that it is unaffected.

## References

- [patch] https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-42321
- [other] https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-42321
- [other] http://packetstormsecurity.com/files/166153/Microsoft-Exchange-Server-Remote-Code-Execution.html
- [other] http://packetstormsecurity.com/files/168131/Microsoft-Exchange-Server-ChainedSerializationBinder-Remote-Code-Execution.html
- [other] https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-42321

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Summary, impact and action are written by the vulneraibility.com AI analysis pipeline from the CVE record, NVD, CISA and FIRST data; verify against the references.