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CVE-2025-66376

79
FAUCET Score

CVE-2025-66376 is a stored Cross-Site Scripting (XSS) vulnerability impacting Zimbra Collaboration (ZCS) versions 10 before 10.0.18 and 10.1 before 10.1.13, enabling attackers to inject malicious code through CSS @import directives within HTML email messages. Rated Medium with a CVSS score of 6.1, this flaw has a network attack vector and low complexity, requiring user interaction to achieve low impacts on confidentiality and integrity. The vulnerability is actively exploited in the wild, listed in CISA's KEV catalog, with reports indicating Russian APT groups are leveraging it against Ukrainian government entities.

Impacted Technologies

VendorProductVersion(s)CPE
>= 10.0, < 10.0.18CPE match
cpe:2.3:a:zimbra:collaboration:*:*:*:*:*:*:*:*
>= 10.1, < 10.1.13CPE match
cpe:2.3:a:zimbra:collaboration:*:*:*:*:*:*:*:*
>= 10.0.0, < 10.0.18CPE matchmatch criteria
cpe:2.3:a:synacor:zimbra_collaboration_suite:*:*:*:*:*:*:*:*
>= 10.1.0, < 10.1.13CPE matchmatch criteria
cpe:2.3:a:synacor:zimbra_collaboration_suite:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.2HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
CHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
2.7
CvssVersion
3.1

Exploit Intelligence

EPSS Score
21.62%
Probability of exploitation in next 30 days
EPSS Percentile
97.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
Added to KEV · Mar 18, 2026
This CVE's current EPSS score of 0.2162 is in the 99th percentile among its peer group of 26,221 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Patches (2)

3cxvendor investigatingvia llm_extracted
inveniosoftwarevendor investigatingvia llm_extracted

Vendor Advisories (2)

inveniosoftwarellm-inveniosoftware-b76c8fad0dcc3ac0MEDIUM

Zimbra Collaboration Suite Cross-Site Scripting (CVE-2025-66376)

Mar 26, 2026
3cxllm-3cx-e581acbfb76ba113MEDIUM

Zimbra Collaboration Suite Cross-Site Scripting (CVE-2025-66376)

Mar 26, 2026

References

cisa.gov / known-exploited-vulnerabilities-catalog
US Government Resource
wiki.zimbra.com / wiki/Security_Center
Release NotesVendor Advisory
wiki.zimbra.com / wiki/Zimbra_Releases/10.0.18
Release Notes
wiki.zimbra.com / wiki/Zimbra_Releases/10.1.13
Release Notes
wiki.zimbra.com / wiki/Zimbra_Responsible_Disclosure_Policy
Product
wiki.zimbra.com / wiki/Zimbra_Security_Advisories
Vendor Advisory