CVE-2021-33766
Microsoft Exchange Server Information Disclosure Vulnerability
- Published
- Updated
- Reserved
- Assigned by
- microsoft
Description
Microsoft Exchange Server Information Disclosure Vulnerability
Exploited in the wild
CISA lists this vulnerability in its Known Exploited Vulnerabilities catalog as Microsoft Exchange Server Information Disclosure.
- Added
- 18 Jan 2022
- Fix due (US federal)
- 1 Feb 2022
- Used by ransomware
- Not known
Apply updates per vendor instructions.
Public exploit
An exploit or proof of concept is public: anyone can try it against an unpatched system. CISA's SSVC rates its exploitation: it is being exploited.
Timeline
ID reserved
By microsoft
- 47 days later
· 47 days later
Published
- 6 months later
· 6 months later
Added to CISA KEV
Known exploited in the wild
- 5 years later
· 5 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| microsoftCNA (assigner) | 3.1 | High7.3 | 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 |
| NVDNVD · Analyzed | 3.1 | High7.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L |
- EPSS (exploitation in 30 days)
- 98.2% · top 0.1% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: active · Automatable: yes · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.3.
Weakness
- Information Disclosure
- CWE-noinfo Not enough information
Affected products
Microsoft · Microsoft Exchange Server 2013 Cumulative Update 23
- affected 15.00.0 – < 15.00.1497.015
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 19
- affected 15.01.0 – < 15.01.2176.012
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 20
- affected 15.01.0 – < 15.01.2242.008
Microsoft · Microsoft Exchange Server 2019 Cumulative Update 8
- affected 15.02.0 – < 15.02.0792.013
Microsoft · Microsoft Exchange Server 2019 Cumulative Update 9
- affected 15.02.0 – < 15.02.0858.010
References (4)
- Microsoft Exchange Server Information Disclosure Vulnerability (opens in a new tab)vendor-advisorypatch
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-33766 (opens in a new tab)x_refsource_MISCx_transferred
- https://www.zerodayinitiative.com/advisories/ZDI-21-798/ (opens in a new tab)x_refsource_MISCx_transferred
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-33766 (opens in a new tab)government-resource
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- CISA KEV catalog (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2021-33766)Record last updated .