CVE-2025-66376 on CISA KEV

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.

01What CISA says about this vulnerability

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.

02Required action — verbatim from 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.

03Notes & references

• wiki.zimbra.com — https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories
• wiki.zimbra.com — https://wiki.zimbra.com/wiki/Security_Center
• wiki.zimbra.com — https://wiki.zimbra.com/wiki/Zimbra_Responsible_Disclosure_Policy
• wiki.zimbra.com — https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.13#Security_Fixes
• wiki.zimbra.com — https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.18#Security_Fixes

04SARA's analyst layer — why this matters

This vulnerability is currently on the CISA KEV list, which CISA only adds CVEs to when there is reliable evidence of active exploitation in the wild. For federal civilian agencies, BOD 22-01 requires remediation by the due date above. For everyone else, KEV is the strongest "patch immediately" signal you can get from public threat intel.

05Affected products (summary)

Vendor	Product	Versions
Zimbra	Collaboration	10.0, 10.1

06Detection

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