CVE-2025-66376

Known Exploited Vulnerability Entry External Catalog

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Entry Details

CVE-2025-66376

Confirmed

Yes

2026-03-18 00:00 UTC

Timestamps

2026-03-18

2026-03-18

Scope

KEV entry: 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

References
  • {'id': 'CVE-2025-66376', 'url': 'https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2025-66376'}

ff5628bd-87ca-43c5-b5a5-913f4b95503c

405284c2-e461-4670-8979-7fd2c9755a60

2026-03-18 18:00 UTC

2026-03-18 18:00 UTC

Evidence (1)
Type Source Signal Confidence Details GCVE Metadata
vendor_report cisa-kev successful_exploitation 0.80
View details 
{
  "cwes": [
    "CWE-79"
  ],
  "date_added": "2026-03-18",
  "due_date": "2026-04-01",
  "feed": "CISA Known Exploited Vulnerabilities Catalog",
  "knownRansomwareCampaignUse": "Unknown",
  "product": "Zimbra Collaboration Suite (ZCS)",
  "vendorProject": "Synacor",
  "vulnerabilityName": "Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting Vulnerability"
}
 -
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