CVE-2025-66376

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

In the wild

CISA lists this as exploited in real attacks. Treat as urgent.

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2025-11-28 00:00 UTC ReservedThe CVE id was reserved by its CNA
2. 2026-01-05 15:15 UTC PublishedDisclosed publicly on CVE.org and NVD
3. 2026-03-18 Exploited in the wildAdded to CISA's Known Exploited Vulnerabilities list
4. 2026-04-01 Remediation deadlineCISA's due date for federal agencies to fix it
5. 2026-10-07 10:10 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: yes, CISA lists it. This puts it above everything that is not.
• Exploit odds: 20.2% in the next 30 days (EPSS).
• Severity: 7.2 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-01-05 15:15 UTC

Last modified

2026-10-07 10:10 UTC

Added to CISA KEV

2026-03-18

Exploit probability

20.2% · EPSS, next 30 days

Weakness

CWE-79 · Cross-site scripting

Record status

Analyzed

Affected

• Synacor Zimbra Collaboration Suite < 10.0.18
• Synacor Zimbra Collaboration Suite < 10.1.13

Attack profile CVSS 3.1 · 7.2

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2025-66376.md and follow it. Check whether this project is affected by CVE-2025-66376. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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