Exploitation evidence
Known exploited · CISA KEV listed
Added 2022-01-18. Ransomware campaign use: Unknown.
CISA required action: Apply updates per vendor instructions.
CISA due date: 2022-02-01. This is the catalog’s deadline, not an assessment of your organization’s exposure.
KEV checked 13 Nov 2026, 00:20 Jerusalem · Original catalog ↗Reported products and versions
Microsoft / Microsoft Exchange Server 2013 Cumulative Update 23
Default status: Not specified
- affected: 15.00.0 to < 15.00.1497.015 (custom)
Microsoft / Microsoft Exchange Server 2016 Cumulative Update 19
Default status: Not specified
- affected: 15.01.0 to < 15.01.2176.012 (custom)
Microsoft / Microsoft Exchange Server 2016 Cumulative Update 20
Default status: Not specified
- affected: 15.01.0 to < 15.01.2242.008 (custom)
Microsoft / Microsoft Exchange Server 2019 Cumulative Update 8
Default status: Not specified
- affected: 15.02.0 to < 15.02.0792.013 (custom)
Microsoft / Microsoft Exchange Server 2019 Cumulative Update 9
Default status: Not specified
- affected: 15.02.0 to < 15.02.0858.010 (custom)
Fixes and workarounds
No explicit solution text in the downloaded CVE record. Consult the vendor advisory; unaffected version ranges are shown above as reported, not inferred as a patch recommendation.
Sources and related reporting
Observed change timeline
History begins when Egret first downloads each source. It is not the complete upstream CVE history.
12 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-12",
"epss": 0.98176,
"percentile": 0.99914
}10 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-10",
"epss": 0.98176,
"percentile": 0.99914
}09 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-09",
"epss": 0.98176,
"percentile": 0.99914
}08 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-08",
"epss": 0.98176,
"percentile": 0.99914
}07 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-07",
"epss": 0.98176,
"percentile": 0.99914
}06 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-06",
"epss": 0.98176,
"percentile": 0.99914
}06 Nov 2026, 06:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-05",
"epss": 0.98176,
"percentile": 0.99914
}05 Nov 2026, 12:20 Jerusalem · CVE Program record changed
Stored CNA snapshot at this observation.
{
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}04 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-04",
"epss": 0.98176,
"percentile": 0.99914
}03 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-03",
"epss": 0.98176,
"percentile": 0.99914
}03 Nov 2026, 02:22 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-02",
"epss": 0.98176,
"percentile": 0.99914
}03 Nov 2026, 02:22 Jerusalem · CISA KEV status changed
Stored KEV snapshot at this observation.
{
"cveID": "CVE-2021-33766",
"cwes": [
"CWE-287"
],
"dateAdded": "2022-01-18",
"dueDate": "2022-02-01",
"forensicTriage": "No",
"knownRansomwareCampaignUse": "Unknown",
"notes": "https://nvd.nist.gov/vuln/detail/CVE-2021-33766",
"product": "Exchange Server",
"requiredAction": "Apply updates per vendor instructions.",
"shortDescription": "Microsoft Exchange Server contains an information disclosure vulnerability which can allow an unauthenticated attacker to steal email traffic from target.",
"vendorProject": "Microsoft",
"vulnerabilityName": "Microsoft Exchange Server Information Disclosure"
}