Executive brief
An unauthenticated calendar sender can place active markup in a COUNTER message's RFC From address. Selecting the message in Zimbra Classic triggers stored XSS, allowing the attacker to access mailbox data and act as the victim.
Junglewise Threat Intelligence
CVE-2026-93647: An unauthenticated calendar sender can place active markup in a COUNTER message's RFC From address. Selecting the message in Zimbra Classic
CVE-2026-93647 · Severity: critical · CVSS 9.3 · Published 2026-09-25