CVE CVE-2025-66376

CVE-2025-66376 — Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting Vulnerability

CISA KEV · Mar 18, 2026 · CRITICAL cve actively-exploited kev
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.
CVSS Score
N/A
CRITICAL
Vendor
Synacor
Product
Zimbra Collaboration Suite (ZCS)

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.

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cve actively-exploited kev
Original Source
CISA KEV
https://www.cisa.gov/known-exploited-vulnerabilities-catalog
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