CVE-2021-33766
Microsoft Exchange Server Information Disclosure Vulnerability
- High 7.3
- Exploited: added to CISA KEV 18 Jan 2022
Description
Microsoft Exchange Server Information Disclosure Vulnerability
Key facts
- Published
- 14 Jul 2021
- Last changed
- 10 Aug 2026
- Assigned by
- microsoft
- KEV added
- 18 Jan 2022
- KEV fix due
- 1 Feb 2022
- EPSS
- 98.176% likely to be exploited in the next 30 days, higher than 99.914% of CVEs (scores for 15 Nov 2026)
- SSVC (CISA)
- Exploitation: active; Automatable: yes; Technical impact: partial
Severity scores
Each score is shown as its source gave it. They are not averaged or merged.
- 7.3CVSS 3.1, Highfrom the CNA (microsoft)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L/E:U/RL:O/RC:C
What to do
- Apply updates per vendor instructions.CISA KEV required action
Historical context and remediation
This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.
No separately sourced impact summary is available on this page yet. Consult the description, version data and dated exploitation evidence.
Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.
Affected products
| Vendor | Product | Versions |
|---|---|---|
| Microsoft | Microsoft Exchange Server 2013 Cumulative Update 23 |
|
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 19 |
|
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 20 |
|
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 8 |
|
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 9 |
|
Timeline
- 14 Jul 2021 Published
- 18 Jan 2022 CVE-2021-33766 added to CISA KEV
- 18 Jan 2022 Added to the CISA KEV catalogue