Reference page — cumulative record through Sunday, October 4, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2025-66376

CVE-2025-66376MEDIUM

Zimbra Collaboration — Synacor Zimbra Collaboration Suite (ZCS)

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   N   R  C  L  L  N    6.1   .2023   97.4   YES

AFFECTED
  Product        Versions  Fixed
  Collaboration  10.0 –    —

TIMELINE
  Nov 28  Reserved by mitre
  Jan 5   Published (CNA: mitre)
  Mar 18  Added to CISA KEV, remediation due 2026-04-01
  Sep 30  RESCORED — CVE-2025-66376 (Zimbra Collaboration). CVSS 7.2 → 6.1 (NVD).

CWE-79 · CNA: mitre · CVSS v3.1 · 6 references · NVD status: Analyzed · KEV due April 1, 2026

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.

Lifecycle

Complete event history — 4 events, chronological
Date	Event	Detail
November 28, 2025	Reserved	Reserved by mitre
January 5, 2026	Published	Published (CNA: mitre)
March 18, 2026	KEV ADDED	Added to CISA KEV, remediation due 2026-04-01
September 30, 2026	RESCORED	RESCORED — CVE-2025-66376 (Zimbra Collaboration). CVSS 7.2 → 6.1 (NVD).

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
Zimbra	Collaboration	—	10.0	—

Weaknesses

CWE-79

References (6)

https://wiki.zimbra.com/wiki/Security_Center [Release Notes, Vendor Advisory]
https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.18#Security_Fixes [Release Notes]
https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.13#Security_Fixes [Release Notes]
https://wiki.zimbra.com/wiki/Zimbra_Responsible_Disclosure_Policy [Product]
https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories [Vendor Advisory]
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-66376 [US Government Resource]

Authoritative record: CVE-2025-66376 at cve.org

Vendors: zimbra

Weaknesses: CWE-79

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2025-66376 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Sunday, October 4, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.