CVE-2025-66376

CVE Enrichment

CVSS: 6.1 MEDIUM
EPSS: 20.23%
EPSS Percentile: 97.42%
CISA KEV: YES — Known Exploited Vulnerability

Description

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.

Technical Details

CVSS Version: 3.1
CNA / NVD Source: cve@mitre.org
Published: 05-Jan-2026 22:15
Last Modified: 07-Oct-2026 17:10
EPSS Date: 2026-10-10
CWE: CWE-79

CVSS Vector


            CVSS:3.1                            AV:N /
                            AC:L /
                            PR:N /
                            UI:R /
                            S:C /
                            C:L /
                            I:L /
                            A:N

CISA KEV Details

Date Added: 2026-03-18
Remediation Due: 2026-04-01
Known Ransomware Campaign Use: Unknown
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.
Notes: https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories ; https://nvd.nist.gov/vuln/detail/CVE-2025-66376

Affected Products / Versions

synacor / zimbra_collaboration_suite
Version / affected range: * · from (inclusive) 10.0.0 · before (exclusive) 10.0.18
cpe:2.3:a:synacor:zimbra_collaboration_suite:*:*:*:*:*:*:*:*
synacor / zimbra_collaboration_suite
Version / affected range: * · from (inclusive) 10.1.0 · before (exclusive) 10.1.13
cpe:2.3:a:synacor:zimbra_collaboration_suite:*:*:*:*:*:*:*:*

References

Last enrichment sync: 11-Oct-2026 12:24
Sources: NVD · FIRST EPSS · CISA KEV
Latest successful provider update; providers refresh independently.

Reported Context (2)

CVE-2025-66376 Recorded Future Identifies 85 High-Impact Vulnerabilities in July, Many Actively Exploited
against Zimbra mailservers for at least five months during 2025, until the issue was patched with CVE-2025-66376. TA488 Used Zimbra XSS Flaw to Steal Emails and Maintain Access

CVE (80)

Malware (5)

People (1)

Threat Actors (10)

MITRE ATT&CK (7)

Vendors (25)

Products (72)

Tools (1)

Industries (6)

Countries (3)

Note: Related entities, including threat actors, malware, CVEs, MITRE ATT&CK techniques, vendors, products, tools, countries, and industries, are shown when they appear in the same reporting. Their presence does not necessarily mean they were targeted, compromised, vulnerable, responsible for the activity, or directly involved in the incident.