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CVE-2025-66376

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

Synacor Zimbra Collaboration Suite (ZCS)Applications & CMS
Open in ThreatlineRecord JSON
CVSS
7.2High
ExploitationExploited in the wildAdded to KEV 18 Mar 2026CISA KEV
Exploit odds (EPSS)20.2%Chance of exploitation activity in the next 30 days, higher than 97% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in10.0.18Also 10.1.13CVE List
Federal deadline1 Apr 2026Remediation due date for US federal agenciesCISA KEV
CISA required actionApply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. CISA KEV

What fixes it

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Timeline

  1. 5 Jan 2026, 00:00 UTCPublishedCVE List
  2. 18 Mar 2026Added to CISA KEVCISA KEV

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.

Text from CVE List

Affected versions 2

  • Collaborationaffected: 10.0 before 10.0.18CVE List
  • Collaborationaffected: 10.1 before 10.1.13CVE List

References 7