# CVE-2021-33766

Microsoft Exchange Server Information Disclosure Vulnerability

- Page: https://www.vulneraibility.com/cve/CVE-2021-33766
- CVSS: 7.3
- Known exploited: yes, in CISA KEV since 2022-01-18; CISA due date 2022-02-01
- EPSS: 98.18% (percentile 99.9)
- Unvetted proof-of-concept code on GitHub: 2 GitHub proofs of concept · 1 Nuclei template (first 2021-08-31)
- CISA SSVC: exploitation active, automatable yes, technical impact partial (assessed 2025-02-04)
- Published: 2021-07-14

## Affected versions

- Microsoft Microsoft Exchange Server 2013 Cumulative Update 23: affected >= 15.00.0 and < 15.00.1497.015
- Microsoft Microsoft Exchange Server 2016 Cumulative Update 19: affected >= 15.01.0 and < 15.01.2176.012
- Microsoft Microsoft Exchange Server 2016 Cumulative Update 20: affected >= 15.01.0 and < 15.01.2242.008
- Microsoft Microsoft Exchange Server 2019 Cumulative Update 8: affected >= 15.02.0 and < 15.02.0792.013
- Microsoft Microsoft Exchange Server 2019 Cumulative Update 9: affected >= 15.02.0 and < 15.02.0858.010

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

## References

- [patch] https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-33766
- [other] https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-33766
- [other] https://www.zerodayinitiative.com/advisories/ZDI-21-798/
- [other] https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-33766

---
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.