Vulnerability
CVE-2025-66376
Synacor Zimbra Collaboration Suite: cross-site scripting
Most severe levelDEFCON 3 · Substantial risk
Official data
- CVSS 3.1
- 6.1 · medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Weakness
- CWE-79
- EPSS
- 20.23% probability of exploitation in the next 30 days, higher than 97% of CVEs
- CISA KEV catalogue
- Yes, since 18 March 2026
Sources: NVD (CVSS, weakness, publication), FIRST (EPSS), CISA (KEV catalogue).
Data read on 4 November 2026.
Timeline
- 5 January 2026Published on NVD
- 18 March 2026Added to the CISA KEV catalogue
- 19 March 2026First in the DefenceLevel briefing
In DefenceLevel briefings3 days
- 21 March 2026Still ongoingDEFCON 4
- 20 March 2026Still ongoingDEFCON 4
- 19 March 2026New in the last 24 hoursDEFCON 3
Last 12 months.
The full analysis is in the briefingThe full analysis is in your archive
Why it matters now, who is affected and what to do: every day at 05:00 UTC, for subscribers.Why it matters, who is affected and what to do, as in the daily briefing.
More exploited Synacor vulnerabilities