What EVULNABLE says
Listed in the CISA KEV catalog, and Confirmed exploitation in the wild.
Patch This Cycle
CVE-2025-66376
Synacor — Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting Vulnerability
CISA KEV · in the CISA KEV catalog since 2026-03-18
The priority band answers “how soon”, not “how bad” — see Methodology for what it weighs and where it abstains.
The evidence behind it
| Measure | Value | Source |
|---|---|---|
| CVSS base score | 6.1 | NVD |
| FIRST EPSS | 0.196 (97.2nd pctl) | FIRST |
| Actively exploited | Confirmed | CISA KEV |
| Ransomware campaign use | Unknown or none | CISA KEV |
| CISA remediation deadline | 2026-04-01 — Overdue by 5 months | CISA KEV |
What CISA says to do
The primary records
This page is an opinion about urgency. Where it and a source of record disagree, the source of record is the record.
Where this sits
CVE-2025-66376 is one of the entries ranked on the priority feed and in the non-Microsoft advisories.