CVE-2025-66376

HIGH CISA KEV

CVSS v3

7.2

HIGH

EPSS Score

0.0%

exploit probability

CISA KEV

Yes

known exploited

Exploitation

—

SSVC status

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.

CISA Known Exploited Vulnerability

Date Added: 3/18/2026
Patch Due Date: 4/1/2026
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.

Technical Details

CVSS v3 Vector: 3.1
Published: 1/5/2026
Last Modified: 1/8/2026

Frequently Asked Questions

What is CVE-2025-66376?

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.

Is CVE-2025-66376 actively exploited?

Yes. CVE-2025-66376 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, meaning it has been confirmed as actively exploited in the wild. CISA requires federal agencies to patch by 4/1/2026.

What is the CVSS score for CVE-2025-66376?

CVE-2025-66376 has a CVSS v3 base score of 7.2 (HIGH severity), with vector string 3.1.

Is CVE-2025-66376 affecting your environment?

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