CVE-2025-66376

moderate-risk
Published 2026-01-05

Zimbra Collaboration (ZCS) 10 before 10.0.18 and 10.1 before 10.1.13 allows Classic UI stored XSS via Cascading Style Sheets (CSS) @import directives in an HTML e-mail message.

Do I need to act?

!
10.0% chance of exploitation in next 30 days
EPSS score — higher than 90% of all CVEs
!
CISA KEV: actively exploited in the wild
On the Known Exploited Vulnerabilities catalog — federal agencies must patch
?
Patch status unknown
Check vendor advisories for fix availability and mitigation guidance
7
CVSS 7.2/10 High
NETWORK / LOW complexity

Affected Products (1)

Affected Vendors

Synacor

References (6)

Release Notes https://wiki.zimbra.com/wiki/Security_Center
Release Notes https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.18#Security_Fixes
Release Notes https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.13#Security_Fixes
Product https://wiki.zimbra.com/wiki/Zimbra_Responsible_Disclosure_Policy
Vendor Advisory https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories
US Government Resource https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-...
49
/ 100
moderate-risk
Severity 26/34 · High
Exploitability 18/34 · Moderate
Exposure 5/34 · Minimal