CVE DATABASE / CVE-2021-33766
CVE-2021-33766
Microsoft Exchange Server Information Disclosure
CVSS 7.3 · HIGH
⚠ CISA KEV — ACTIVELY EXPLOITED
On the CISA KEV catalog
Confirmed exploited in the wild. Added 2022-01-18.
Federal remediation due 2022-02-01.
Required action: Apply updates per vendor instructions.
Summary
Microsoft Exchange Server Information Disclosure Vulnerability
CVSS 3.1 breakdown
| Base score | 7.3 (HIGH) |
| Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L |
| Attack vector | NETWORK |
| Attack complexity | LOW |
| Privileges required | NONE |
| User interaction | NONE |
| Scope | UNCHANGED |
| Confidentiality | LOW |
| Integrity | LOW |
| Availability | LOW |
Affected products
Microsoft exchange server
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References
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-33766
- https://www.zerodayinitiative.com/advisories/ZDI-21-798/
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-33766
Data: NIST NVD + CISA KEV. NVD last modified 2025-10-29. Always verify against the vendor advisory before acting.