CVE-2026-33368: Synacor Zimbra Collaboration Suite

Medium severity, CVSS 6.1. EPSS: 0.4% chance of exploitation in the next 30 days.

Zimbra Collaboration Suite (ZCS) 10.0 and 10.1 contains a reflected cross-site scripting (XSS) vulnerability in the Classic Webmail REST interface (/h/rest). The application fails to properly sanitize user-supplied input, allowing an unauthenticated attacker to inject malicious JavaScript into a crafted URL. When a victim user accesses the link, the injected script executes in the context of the Zimbra webmail application, which could allow the attacker to perform actions on behalf of the victim.

Affected products

• Synacor Zimbra Collaboration Suite: from 10.0.0, before 10.1.16 (fixed in 10.1.16)

Published 2026-03-20. Last modified 2026-06-17.