# CVE-2021-33766: Microsoft Exchange Server Information Disclosure Vulnerability

CVE-2021-33766 is fixed in 5 products on 1 platform, first by KB5001779, released April 13, 2021. It is being exploited: CISA added it to the Known Exploited Vulnerabilities catalog on January 18, 2022. Patch Radar priority: Patch now.

- Web page: https://patchblox.com/security/cve/CVE-2021-33766
- Priority: Patch now
- CVSS: 7.3 (Important)
- EPSS: 0.9818
- CISA KEV: listed Jan 18, 2022, federal due date Feb 1, 2022
- Exploited (vendor report): no
- Publicly disclosed: no
- Vendor exploitability assessment: Exploitation Less Likely
- Published: Jul 13, 2021
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-33766

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Microsoft | Microsoft Exchange Server 2013 Cumulative Update 23 |  | [KB5001779](https://patchblox.com/security/data/fix/microsoft/kb5001779.md) | Apr 13, 2021 |
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 19 |  | [KB5001779](https://patchblox.com/security/data/fix/microsoft/kb5001779.md) | Apr 13, 2021 |
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 20 |  | [KB5001779](https://patchblox.com/security/data/fix/microsoft/kb5001779.md) | Apr 13, 2021 |
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 8 |  | [KB5001779](https://patchblox.com/security/data/fix/microsoft/kb5001779.md) | Apr 13, 2021 |
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 9 |  | [KB5001779](https://patchblox.com/security/data/fix/microsoft/kb5001779.md) | Apr 13, 2021 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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