CVEs / CVE-2021-33766
CVE-2021-33766: Microsoft Exchange Server Information Disclosure
- Known exploited in the CISA KEV catalog since 18 Jan 2022
- medium 5 CVSS 2.0 (NVD)
- EPSS 98.1% chance of exploitation in the next 30 days, higher than 99% of CVEs (30 Oct 2026)
- Last changed at its sources
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Summary
Microsoft Exchange Server contains an information disclosure vulnerability which can allow an unauthenticated attacker to steal email traffic from target.
Description
Microsoft Exchange Server Information Disclosure Vulnerability
Affected and fixed versions
| Product | Affected | Fixed in |
|---|---|---|
| Microsoft Microsoft Exchange Server 2013 Cumulative Update 23 | from 15.00.0, before 15.00.1497.015 | 15.00.1497.015 |
| Microsoft Microsoft Exchange Server 2016 Cumulative Update 19 | from 15.01.0, before 15.01.2176.012 | 15.01.2176.012 |
| Microsoft Microsoft Exchange Server 2016 Cumulative Update 20 | from 15.01.0, before 15.01.2242.008 | 15.01.2242.008 |
| Microsoft Microsoft Exchange Server 2019 Cumulative Update 8 | from 15.02.0, before 15.02.0792.013 | 15.02.0792.013 |
| Microsoft Microsoft Exchange Server 2019 Cumulative Update 9 | from 15.02.0, before 15.02.0858.010 | 15.02.0858.010 |
Exploitation
| In CISA KEV since | 18 Jan 2022 |
|---|---|
| Due date for US federal agencies | 1 Feb 2022 |
| Used in ransomware campaigns | Unknown |
| Required action | Apply updates per vendor instructions. |
Severity
| CVSS 2.0 | 5 mediumAV:N/AC:L/Au:N/C:P/I:N/A:NScored by NVD |
|---|
References
- CVE-2021-33766 on NVD
- CVE-2021-33766 in the CISA KEV catalog
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-33766 Patch, Vendor Advisory
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-33766 Patch, 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-2021-33766 US Government Resource
Sources
Exploitation status from the CISA Known Exploited Vulnerabilities catalog. EPSS scores from FIRST. Descriptions, severity and references from the National Vulnerability Database. Open-source package versions from OSV (CC-BY 4.0). Text is shown as each source states it; Stackurity does not edit it. Check the vendor's advisory before acting.
This product uses data from the NVD API but is not endorsed or certified by the NVD.