Exploitation evidence
Known exploited · CISA KEV listed
Added 2026-03-18. Ransomware campaign use: Unknown.
CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
CISA due date: 2026-04-01. 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
Zimbra / Collaboration
Default status: unaffected
- affected: 10.0 to < 10.0.18 (custom)
- affected: 10.1 to < 10.1.13 (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
CVE Program record ↗ · Download tracked evidence as JSON
- https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories
- https://wiki.zimbra.com/wiki/Security_Center
- https://wiki.zimbra.com/wiki/Zimbra_Responsible_Disclosure_Policy
- https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.13#Security_Fixes
- https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.18#Security_Fixes
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-66376
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": 0.20227,
"percentile": 0.97503
}10 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-10",
"epss": 0.20227,
"percentile": 0.97487
}09 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-09",
"epss": 0.20227,
"percentile": 0.97484
}08 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-08",
"epss": 0.20227,
"percentile": 0.97483
}07 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-07",
"epss": 0.20227,
"percentile": 0.97482
}06 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-06",
"epss": 0.20227,
"percentile": 0.97479
}06 Nov 2026, 06:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-05",
"epss": 0.20227,
"percentile": 0.97476
}04 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-04",
"epss": 0.20227,
"percentile": 0.97474
}03 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-03",
"epss": 0.20227,
"percentile": 0.9747
}03 Nov 2026, 12:20 Jerusalem · CVE Program record changed
Stored CNA snapshot at this observation.
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2025-66376",
"options": [
{
"Exploitation": "active"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-03-17T00:00:00+00:00",
"version": "2.0.3"
},
"type": "ssvc"
}
},
{
"other": {
"content": {
"dateAdded": "2026-03-18",
"reference": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-66376"
},
"type": "kev"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-03-19T03:55:17.926Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"references": [
{
"tags": [
"government-resource"
],
"url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-66376"
}
],
"timeline": [
{
"lang": "en",
"time": "2026-03-18T00:00:00.000Z",
"value": "CVE-2025-66376 added to CISA KEV"
}
],
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Collaboration",
"vendor": "Zimbra",
"versions": [
{
"lessThan": "10.0.18",
"status": "affected",
"version": "10.0",
"versionType": "custom"
},
{
"lessThan": "10.1.13",
"status": "affected",
"version": "10.1",
"versionType": "custom"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:zimbra:collaboration:*:*:*:*:*:*:*:*",
"versionEndExcluding": "10.0.18",
"versionStartIncluding": "10.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:a:zimbra:collaboration:*:*:*:*:*:*:*:*",
"versionEndExcluding": "10.1.13",
"versionStartIncluding": "10.1",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "Zimbra Collaboration (ZCS) 10 before 10.0.18 and 10.1 before 10.1.13 allows Classic UI stored XSS via Cascading Style Sheets (CSS) @import directives in an HTML e-mail message."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.2,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N",
"version": "3.1"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-79",
"description": "CWE-79 Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting')",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-01-05T14:49:53.107Z",
"orgId": "8254265b-2729-46b6-b9e3-3dfca2d5bfca",
"shortName": "mitre"
},
"references": [
{
"url": "https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories"
},
{
"url": "https://wiki.zimbra.com/wiki/Security_Center"
},
{
"url": "https://wiki.zimbra.com/wiki/Zimbra_Responsible_Disclosure_Policy"
},
{
"url": "https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.13#Security_Fixes"
},
{
"url": "https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.18#Security_Fixes"
}
],
"x_generator": {
"engine": "enrichogram 0.0.1"
}
}
},
"cveMetadata": {
"assignerOrgId": "8254265b-2729-46b6-b9e3-3dfca2d5bfca",
"assignerShortName": "mitre",
"cveId": "CVE-2025-66376",
"datePublished": "2026-01-05T00:00:00.000Z",
"dateReserved": "2025-11-28T00:00:00.000Z",
"dateUpdated": "2026-03-19T03:55:17.926Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}03 Nov 2026, 02:22 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-02",
"epss": 0.20227,
"percentile": 0.97466
}03 Nov 2026, 02:22 Jerusalem · CISA KEV status changed
Stored KEV snapshot at this observation.
{
"cveID": "CVE-2025-66376",
"cwes": [
"CWE-79"
],
"dateAdded": "2026-03-18",
"dueDate": "2026-04-01",
"forensicTriage": "No",
"knownRansomwareCampaignUse": "Unknown",
"notes": "https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories ; https://nvd.nist.gov/vuln/detail/CVE-2025-66376",
"product": "Zimbra Collaboration Suite (ZCS)",
"requiredAction": "Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.",
"shortDescription": "Synacor Zimbra Collaboration Suite (ZCS) contains a cross-site scripting vulnerability in the Classic UI where attackers could abuse Cascading Style Sheets (CSS) @import directives in email HTML.",
"vendorProject": "Synacor",
"vulnerabilityName": "Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting Vulnerability"
}