CVE-2025-66376 — Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting Vulnerability
2026-03-18 • CISA Known Exploited Vulnerability
[event] 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 SOFTWARE
| Field | Value |
|---|---|
| Vendor | Synacor |
| Product | Zimbra Collaboration Suite (ZCS) |
| CWE | CWE-79 |
| CVE ID | CVE-2025-66376 |
| Date Added | 2026-03-18 |
| Due Date | 2026-04-01 |
| Ransomware Campaign | Unknown |
> MITIGATION
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Due Date: 2026-04-01