CVE-2025-66376

HIGHCVSS 7.2Known Exploited

CISA Known Exploited Vulnerability

https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories ; https://nvd.nist.gov/vuln/detail/CVE-2025-66376

Remediation deadline: April 1, 2026

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.

Timeline

Published:January 5th, 2026 3:15 PM

Last modified:October 7th, 2026 10:10 AM

Added to KEV:March 18th, 2026

CVSS Scoring

CVSS v3: 7.2 (HIGH)

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

Affected Software

From NVD CPE configuration data

Vendors

synacor

Products

zimbra_collaboration_suite

Weaknesses (CWE)

CWE-79

References & Reports

Advisories, patches, and third-party reports

https://wiki.zimbra.com/wiki/Security_CenterRelease Notes
https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.18#Security_FixesRelease Notes
https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.13#Security_FixesRelease Notes
https://wiki.zimbra.com/wiki/Zimbra_Responsible_Disclosure_PolicyProduct
https://wiki.zimbra.com/wiki/Zimbra_Security_AdvisoriesVendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-66376US Government Resource

Source: NIST NVD · Data may lag official sources by up to one minute