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    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.

    Published:Jan 5, 2026
    Last Modified:Mar 19, 2026
    EPS:Jan 5, 2026
    EPSS Score:0.00049
    CVSS Score:7.2

    CISA Notification

    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.

    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:

    No extra notes provided.

    Due Date
    Apr 1, 2026
    163 days ago
    Alert Date
    Mar 18, 2026
    177 days ago

    Affected Products

    Vendor
    Synacor
    Product
    Zimbra Collaboration Suite
    Vendor
    Zimbra
    Product
    Collaboration

    Exploits

    No exploit reference

    Related CVEs

    CVE-2026-73576 (CVSS 6.3) — In Zimbra Collaboration (ZCS) before 10.1.17, weak cryptographic key generation vulnerability exists in the On…
    CVE-2026-73575 (CVSS 3.1) — In Zimbra Collaboration (ZCS) before 10.1.17, a Cross-Site Request Forgery (CSRF) vulnerability exists in the …
    CVE-2026-73574 (CVSS 3.1) — In Zimbra Collaboration before 10.1.17, a local file inclusion (LFI) vulnerability exists in the Zimbra Classi…
    CVE-2026-73573 (CVSS 3.1) — In Zimbra Collaboration (ZCS) before 10.1.17, a path traversal vulnerability exists in the Zimbra Briefcase do…
    CVE-2026-73572 (CVSS 6.1) — In Zimbra Collaboration (ZCS) before 10.1.17, a stored cross-site scripting (XSS) vulnerability exists in the …
    CVE-2026-73571 (CVSS 3.1) — An authorization bypass vulnerability exists in Zimbra Collaboration (ZCS) before 10.1.17 due to improper auth…
    CVE-2026-73570 (CVSS 8.9) — A remote code execution vulnerability exists in Zimbra Collaboration (ZCS) before 10.1.20 when the optional zi…
    CVE-2026-33373 (CVSS 8.8) — An issue was discovered in Zimbra Collaboration (ZCS) 10.0 and 10.1. A Cross-Site Request Forgery (CSRF) vulne…
    CVE-2026-33372 (CVSS 5.4) — An issue was discovered in Zimbra Collaboration (ZCS) 10.0 and 10.1. A cross-site request forgery (CSRF) vulne…
    CVE-2026-33370 (CVSS 6.1) — An issue was discovered in Zimbra Collaboration (ZCS) 10.0 and 10.1. A stored cross-site scripting (XSS) vulne…

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High