CVE-2025-66376
Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting Vulnerability
What is affected
| Vendor | Synacor |
|---|---|
| Product | Zimbra Collaboration Suite (ZCS) |
| Weakness | CWE-79 |
The vulnerability
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.
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.
US federal civilian agencies were required to act by 1 April 2026 under BOD 22-01. The deadline is a compliance date, not a measure of severity — it says nothing about how dangerous the flaw is to anyone else.
Where this comes from
Every field on this page is taken from the CISA Known Exploited Vulnerabilities catalog, last synced 13 Nov 2026, 12:31. Nothing here is our own assessment. For the technical scoring, see the NVD record below.
More from Synacor
Synacor Zimbra Collaboration Suite (ZCS)
Zimbra Collaboration Suite (ZCS) OS Command Injection Vulnerability
CVE-2025-48700Synacor Zimbra Collaboration Suite (ZCS)
Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
CVE-2020-7796Synacor Zimbra Collaboration Suite
Synacor Zimbra Collaboration Suite (ZCS) Server-Side Request Forgery Vulnerability
CVE-2025-68645Synacor Zimbra Collaboration Suite (ZCS)
Synacor Zimbra Collaboration Suite (ZCS) PHP Remote File Inclusion Vulnerability