Vulnerability record

CVE-2025-66376

A permanent, source-backed tracker page. Values are shown only when returned; explicit gaps and read failures remain different states.

Full record read. Reported values and explicit gaps below come from the tracked record. Tracker snapshot: Aug 9, 2026.

What it is

Reported

Synacor Zimbra Collaboration Suite (ZCS) contains a cross-site scripting vulnerability in the Classic UI where attackers could abuse Cascading Style Sheets (CSS) @import directives in email HTML. Source description excerpt; complete tracked detail loads below.

NVD published: Jan 5, 2026 · Source record updated: Aug 9, 2026 · Tracker snapshot: Aug 9, 2026

What is affected

Reported

Synacor — Zimbra Collaboration Suite (ZCS). Product-level identification only; no affected-version conclusion is available from this field.

NVD published: Jan 5, 2026 · Source record updated: Aug 9, 2026 · Tracker snapshot: Aug 9, 2026

Urgency and basis

Reported

Act · 460.8

Tracker decision tier from the evidence detailed below · Source record updated: Aug 9, 2026 · Tracker snapshot: Aug 9, 2026

Exploitation evidence

Reported

kev-listed · CISA KEV · VulnCheck KEV · ENISA exploited-vulnerability catalog

Active since: Mar 18, 2026 · CISA KEV added: Mar 18, 2026 · VulnCheck KEV added: Mar 17, 2026 · ENISA added: Mar 18, 2026 · Source record updated: Aug 9, 2026 · Tracker snapshot: Aug 9, 2026

What to do

Reported

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Source remediation ↗

Tracked source remediation field · Source record updated: Aug 9, 2026 · Tracker snapshot: Aug 9, 2026

Evidence detail

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