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High 7.3Known exploited (CISA KEV)Published Jul 14, 2021
CVE-2021-33766Microsoft Exchange Server Information Disclosure Vulnerability
Updated under an hour ago ()
Does this affect you?
It affects Microsoft Exchange Server 2013 Cumulative Update 23 and 5 other products. Add what you run to find out whether that includes you.
CISA lists it as known exploited since Jan 18, 2022; federal agencies had to remediate by Feb 1, 2022. Treat that date as your deadline.
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Microsoft Exchange Server Information Disclosure Vulnerability
- CVSS
- 7.3 HIGH (v3.1, CNA)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
- Weakness (CWE)
- Not given
- Known exploited
- Added to CISA KEV Jan 18, 2022; federal remediation due Feb 1, 2022Apply updates per vendor instructions.
- EPSS (exploitation in the next 30 days)
- 98.18% (percentile 100)
- Assigned by
- microsoft
- NVD analysis
- Analyzed
- Record last updated
- Aug 10, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Microsoft Microsoft Exchange Server 2013 Cumulative Update 23 microsoft:exchange_server_2013_cumulative_update_23 (from the name) | from 15.00.0 before 15.00.1497.015 | CNA record |
Microsoft Microsoft Exchange Server 2016 Cumulative Update 19 microsoft:exchange_server_2016_cumulative_update_19 (from the name) | from 15.01.0 before 15.01.2176.012 | CNA record |
Microsoft Microsoft Exchange Server 2016 Cumulative Update 20 microsoft:exchange_server_2016_cumulative_update_20 (from the name) | from 15.01.0 before 15.01.2242.008 | CNA record |
Microsoft Microsoft Exchange Server 2019 Cumulative Update 8 microsoft:exchange_server_2019_cumulative_update_8 (from the name) | from 15.02.0 before 15.02.0792.013 | CNA record |
Microsoft Microsoft Exchange Server 2019 Cumulative Update 9 microsoft:exchange_server_2019_cumulative_update_9 (from the name) | from 15.02.0 before 15.02.0858.010 | CNA record |
microsoft exchange_server microsoft:exchange_server | 2013; 2016; 2016; 2019; 2019 | NVD |
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-33766vendor-advisory, patch
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-33766patch, vendor-advisory
- https://www.zerodayinitiative.com/advisories/ZDI-21-798/third-party-advisory, vdb-entry
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-33766us-government-resource
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.