CVE-2026-73571: Synacor Zimbra Collaboration Suite

Medium severity, CVSS 4.3. EPSS: 0.3% chance of exploitation in the next 30 days.

An authorization bypass vulnerability exists in Zimbra Collaboration (ZCS) before 10.1.17 due to improper authorization validation in delegated email sending functionality. An authenticated attacker can send specially crafted SOAP requests to impersonate another user and send emails without possessing the required delegation or send-as permissions. This occurs in the SaveDraftRequest SOAP handler.

Affected products

• Synacor Zimbra Collaboration Suite: before 10.1.17 (fixed in 10.1.17)

Published 2026-08-13. Last modified 2026-08-28.