CVE DATABASE / CVE-2025-66376
CVE-2025-66376
Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting Vulnerability
Confirmed exploited in the wild. Added 2026-03-18.
Federal remediation due 2026-04-01.
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.
Summary
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.
CVSS 3.1 breakdown
| Base score | 7.2 (HIGH) |
| Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N |
| Attack vector | NETWORK |
| Attack complexity | LOW |
| Privileges required | NONE |
| User interaction | NONE |
| Scope | CHANGED |
| Confidentiality | LOW |
| Integrity | LOW |
| Availability | NONE |
Weakness type (CWE)
Affected products
Use our free CVE Lookup tool for the latest NVD record, or browse the full CISA KEV catalog.
References
- 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
Data: NIST NVD + CISA KEV. NVD last modified 2026-03-18. Always verify against the vendor advisory before acting.