7.3

CVE-2021-33766: Microsoft Exchange Server Information Disclosure

CVSS: 7.3v3.1HighKEVAnalyzed
Published 14-07-2021Last modified 10-08-2026
Open JSON

Vulnerability summary

CVE-2021-33766 is a high (CVSS 7.3) vulnerability in Microsoft Exchange Server. It is known to be exploited: CISA lists it, first on 18-01-2022. EPSS estimates a 98.18% chance of exploitation in the next 30 days, higher than 99.9% of scored vulnerabilities.

Overall risk
85/100
0100
Critical · default modelHow is this calculated?
CVSS score
7.3/10
010
High · v3.1 (CVE.org)
EPSS score
98.18%
0%100%
Critical · +0.04 pp in 30 days
KEVListedCISA
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 14-07-2021
    PublishedVulnerability first disclosed.
  2. 18-01-2022
    Added to CISA KEVMicrosoft Exchange Server Information Disclosure
  3. 01-02-2022
    CISA remediation dueApply updates per vendor instructions.
  4. 10-08-2026
    Last modifiedVulnerability information updated.

Description

Microsoft Exchange Server Information Disclosure Vulnerability

CVSS metrics

3 scores · 2 sources · 2 versions

EPSS trend

Probability

98.18%

Chance of exploitation in the next 30 days

Percentile

100%

Versus all other CVEs

30-day change

+0.04 pp

From 98.14% on 20-09-2026

20-09-202620-10-2026
EPSS score
98.18%

Known exploited

Compare KEV catalogs
CISA KEVListed
Added
18-01-2022
Federal due date
01-02-2022

CISA required action

Apply updates per vendor instructions. nvd.nist.gov/vuln/detail/CVE-2021-33766

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

No weakness data has been published for this record.

Affected systems

Microsoft6 products

1 vendor · 6 products

References

4 links