CVE-2025-48700
Published 2025-06-23 · Updated 2026-06-17 · Source cve@mitre.org
Summary
CVE-2025-48700 is a medium-severity (CVSS 6.1) vulnerability in Synacor Zimbra Collaboration Suite (ZCS). CISA added it to the Known Exploited Vulnerabilities catalog on April 20, 2026, which means exploitation in the wild has been confirmed; US federal agencies had to remediate it by April 23, 2026. CISA does not currently list it as used in ransomware campaigns. Synacor has 19 vulnerabilities in the KEV catalog, 6 of them linked to ransomware.
All 19 known-exploited Synacor vulnerabilities →Description
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.
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CISA Known-Exploited Vulnerability
Product: Synacor — Zimbra Collaboration Suite (ZCS)
Name: Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
Date added: 2026-04-20 · Due: 2026-04-23
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.