CVE-2025-66376
medium CISA KEVSynacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting Vulnerability
Vendor / product: Synacor — Zimbra Collaboration Suite (ZCS)
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
6.1
6.1 (CVSS v3.1)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Severity source: NVD CVSS v3.1 (nvd@nist.gov)
Timeline (UTC)
Published: 2026-01-05 15:15
Modified: 2026-10-07 10:10
NVD status: Analyzed
Last synced 1 day ago
Verified against the source API 2026-10-27 07:07 UTC
Exploitation
Listed in CISA KEV
Added 2026-03-18 · due 2026-04-01
Known ransomware use: Unknown
Required action (CISA)
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Affected products
synacor / zimbra_collaboration_suite ≥10.0.0 <10.0.18, ≥10.1.0 <10.1.13
Weakness classification (CWE)
Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.
Mitigation & advisories
Vendor advisory: https://wiki.zimbra.com/wiki/Security_Center
Vendor advisory: https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories
References
- https://wiki.zimbra.com/wiki/Security_Center cve@mitre.org
- https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.18#Security_Fixes cve@mitre.org
- https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.13#Security_Fixes cve@mitre.org
- https://wiki.zimbra.com/wiki/Zimbra_Responsible_Disclosure_Policy cve@mitre.org
- https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories cve@mitre.org
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-66376 134c704f-9b21-4f2e-91b3-4a467353bcc0
Data sources
CISA KEV — fetched 2026-10-27 06:50 UTC · record ↗
NVD CVE API 2.0 — fetched 2026-10-27 07:07 UTC · record ↗