high7.2Known exploited
CVE-2025-66376
Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting Vulnerability
Exploited in the wild
This vulnerability is on the CISA Known Exploited Vulnerabilities list, added 2026-03-18. Federal due date: 2026-04-01.
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Impact
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.
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Synacor | Zimbra Collaboration Suite | from 10.0.0 before 10.0.18 from 10.1.0 before 10.1.13 |
Weakness classification
References
- NVD record
- CVE.org record
- CISA KEV catalog
- https://wiki.zimbra.com/wiki/Security_Center
- https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.18#Security_Fixes
- https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.13#Security_Fixes
- https://wiki.zimbra.com/wiki/Zimbra_Responsible_Disclosure_Policy
- https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-66376