CVE-2025-66376 (GCVE-0-2025-66376)
Vulnerability from cvelistv5 – Published: 2026-01-05 00:00 – Updated: 2026-03-19 03:55Summary
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.
Severity
7.2 (High)
SSVC
Exploitation: active
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-03-17 00:00 UTC
CWE
- CWE-79 - Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting')
Assigner
References
6 references
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Zimbra | Collaboration |
Affected:
10.0 , < 10.0.18
(custom)
Affected: 10.1 , < 10.1.13 (custom) cpe:2.3:a:zimbra:collaboration:*:*:*:*:*:*:*:* cpe:2.3:a:zimbra:collaboration:*:*:*:*:*:*:*:* |
CISA
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: b45ecc59-5dc6-4934-945f-727dc39eafbb
Exploited: Yes
Timestamps
First Seen: 2026-03-18
Asserted: 2026-03-18
Scope
Notes: Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting Vulnerability | Affected: Synacor / Zimbra Collaboration Suite (ZCS) | Description: 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. | 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. | Due date: 2026-04-01 | Known ransomware campaign use (KEV): Unknown | Notes (KEV): https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories ; https://nvd.nist.gov/vuln/detail/CVE-2025-66376
Evidence
Type: Vendor Report
Signal: Successful Exploitation
Confidence: 80%
Source: cisa-kev
Details
| Cwes | CWE-79 |
|---|---|
| Feed | CISA Known Exploited Vulnerabilities Catalog |
| Product | Zimbra Collaboration Suite (ZCS) |
| Due Date | 2026-04-01 |
| Date Added | 2026-03-18 |
| Vendorproject | Synacor |
| Vulnerabilityname | Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting Vulnerability |
| Knownransomwarecampaignuse | Unknown |
References
Created: 2026-10-02 08:09 CEST
| Updated: 2026-10-02 08:09 CEST
Previdian
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: 46135b25-a20b-4072-ab5c-77af258ba11b
Exploited: Yes
Timestamps
First Seen: 2026-06-01
Asserted: 2026-06-01
Scope
Notes: 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... | Affected: Zimbra / Collaboration | CVSS: 7.2 (HIGH) | EPSS: 0.19559 | Used in malware: unknown | Listed 1 day ahead of CISA KEV | Not yet in CISA KEV: False
Evidence
Type: Public Report
Signal: Successful Exploitation
Confidence: 70%
Source: previdian
Details
| Feed | Previdian (previdian.com) |
|---|---|
| Title | 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... |
| Cve Id | CVE-2025-66376 |
| Vendor | Zimbra |
| Ghsa Id | GHSA-H7WG-85FJ-3C6G |
| Product | Collaboration |
| Added Date | 2026-06-01T12:10:26.616Z |
| Cvss Score | 7.2 |
| Epss Score | 0.19559 |
| Previous Ids | |
| Cvss Severity | HIGH |
| Virtual Patch | False |
| Cvss Estimated | False |
| Epss Percentile | 0.97307 |
| Used In Malware | unknown |
| Vulnerability Id | CVE-2025-66376 |
| Ahead Of Cisa Kev |
|
| Not Yet In Cisa Kev | False |
References
Created: 2026-10-02 09:09 CEST
| Updated: 2026-10-02 09:09 CEST
{
"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 \u0027Cross-site Scripting\u0027)",
"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",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2025-66376",
"date": "2026-10-01",
"epss": "0.19559",
"percentile": "0.97307"
},
"nvd": {
"cve": {
"affected": [
{
"affectedData": [
{
"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"
}
]
}
],
"source": "cve@mitre.org"
}
],
"cisaActionDue": "2026-04-01",
"cisaExploitAdd": "2026-03-18",
"cisaRequiredAction": "Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.",
"cisaVulnerabilityName": "Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting Vulnerability",
"configurations": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:synacor:zimbra_collaboration_suite:*:*:*:*:*:*:*:*",
"matchCriteriaId": "7D423DB3-FCD4-445F-A778-BC5F83E01953",
"versionEndExcluding": "10.0.18",
"versionStartIncluding": "10.0.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:a:synacor:zimbra_collaboration_suite:*:*:*:*:*:*:*:*",
"matchCriteriaId": "7C3F6B1E-1671-461B-A093-7B6854C227FE",
"versionEndExcluding": "10.1.13",
"versionStartIncluding": "10.1.0",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"cveTags": [],
"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."
},
{
"lang": "es",
"value": "Zimbra Collaboration (ZCS) 10 anterior a 10.0.18 y 10.1 anterior a 10.1.13 permite XSS almacenado en la interfaz de usuario cl\u00e1sica a trav\u00e9s de directivas @import de Hojas de Estilo en Cascada (CSS) en un mensaje de correo electr\u00f3nico HTML."
}
],
"id": "CVE-2025-66376",
"lastModified": "2026-09-30T23:10:00.237",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 7.2,
"baseSeverity": "HIGH",
"confidentialityImpact": "LOW",
"integrityImpact": "LOW",
"privilegesRequired": "NONE",
"scope": "CHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N",
"version": "3.1"
},
"exploitabilityScore": 3.9,
"impactScore": 2.7,
"source": "cve@mitre.org",
"type": "Secondary"
},
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 6.1,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "LOW",
"integrityImpact": "LOW",
"privilegesRequired": "NONE",
"scope": "CHANGED",
"userInteraction": "REQUIRED",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
"version": "3.1"
},
"exploitabilityScore": 2.8,
"impactScore": 2.7,
"source": "nvd@nist.gov",
"type": "Primary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2025-66376",
"options": [
{
"exploitation": "active"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-03-17T00:00:00+00:00",
"version": "2.0.3"
}
}
]
},
"published": "2026-01-05T15:15:44.903",
"references": [
{
"source": "cve@mitre.org",
"tags": [
"Release Notes",
"Vendor Advisory"
],
"url": "https://wiki.zimbra.com/wiki/Security_Center"
},
{
"source": "cve@mitre.org",
"tags": [
"Release Notes"
],
"url": "https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.18#Security_Fixes"
},
{
"source": "cve@mitre.org",
"tags": [
"Release Notes"
],
"url": "https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.13#Security_Fixes"
},
{
"source": "cve@mitre.org",
"tags": [
"Product"
],
"url": "https://wiki.zimbra.com/wiki/Zimbra_Responsible_Disclosure_Policy"
},
{
"source": "cve@mitre.org",
"tags": [
"Vendor Advisory"
],
"url": "https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories"
},
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"tags": [
"US Government Resource"
],
"url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-66376"
}
],
"sourceIdentifier": "cve@mitre.org",
"vulnStatus": "Analyzed",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-79"
}
],
"source": "cve@mitre.org",
"type": "Secondary"
}
]
}
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2025-66376",
"options": [
{
"Exploitation": "active"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-03-18T16:58:05.651376Z",
"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": "2026-01-05T20:42:37.847Z",
"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 \u0027Cross-site Scripting\u0027)",
"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"
}
}
}
Loading…
Loading…
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Loading…
Loading…
The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Loading…
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
Loading…