CVE-2025-48700: Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability

Medium severity, CVSS 6.1. Actively exploited: in CISA KEV since 2026-04-20. EPSS: 1.7% chance of exploitation in the next 30 days.

An issue was discovered in Zimbra Collaboration (ZCS) 8.8.15 and 9.0 and 10.0 and 10.1. A Cross-Site Scripting (XSS) vulnerability in the Zimbra Classic UI allows attackers to execute arbitrary JavaScript within the user's session, potentially leading to unauthorized access to sensitive information. This issue arises from insufficient sanitization of HTML content, specifically involving crafted tag structures and attribute values that include an @import directive and other script injection vectors. The vulnerability is triggered when a user views a crafted e-mail message in the Classic UI, requiring no additional user interaction.

Affected products

• Synacor Zimbra Collaboration Suite: from 10.0.0, before 10.0.12 (fixed in 10.0.12); from 10.1.0, before 10.1.4 (fixed in 10.1.4); version 8.8.15 only; version 9.0.0 only

Published 2025-06-23. Last modified 2026-06-17.