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CVE-2025-66376

KEV

Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting Vulnerability

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Vendor / Project
Synacor
Product
Zimbra Collaboration Suite (ZCS)
Date added
Mar 18, 2026
Due date
Apr 1, 2026
Known ransomware use
Unknown
CWEs
CWE-79

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.

Notes