Is CVE-2026-93628 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-93628 being exploited in the wild.

How severe is CVE-2026-93628?

Medium severity, with a CVSS score of 5.3, published 23 October 2026.

Which products and versions are affected?

Zimbra Collaboration Suite 10.1.16, 10.1.21.

Is there a fix for CVE-2026-93628?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

How is CVE-2026-93628 attacked?

It is attacked over the network, in a hosted service.

Am I affected by CVE-2026-93628?

Check whether you run Zimbra Collaboration Suite at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-93628: Zimbra Collaboration Suite attendee authentication bypass in calendar processing

CVE-2026-93628 · Severity: medium · CVSS 5.3 · Published 2026-10-23

Zimbra Collaboration Suite is an enterprise mail and calendar server used by organizations for email, scheduling, and file sharing. This vulnerability allows an attacker who knows a meeting's identifier, organizer, and attendee email addresses to forge calendar responses that automatically change an attendee's participation status without their knowledge or approval. The attacker needs no account or password and can manipulate meeting attendance across the organization.

Technologies: Zimbra Collaboration Suite. Vendors: Zimbra.

Quick answers

Is CVE-2026-93628 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-93628 being exploited in the wild.
How severe is CVE-2026-93628?: Medium severity, with a CVSS score of 5.3, published 23 October 2026.
Which products and versions are affected?: Zimbra Collaboration Suite 10.1.16, 10.1.21.
Is there a fix for CVE-2026-93628?: No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-93628 attacked?: It is attacked over the network, in a hosted service.
Am I affected by CVE-2026-93628?: Check whether you run Zimbra Collaboration Suite at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

An authentication vulnerability in Zimbra's iCalendar REPLY processing causes a null sender identity to be passed when handling calendar responses, bypassing the attendee authorization filter. An unauthenticated attacker can craft a non-outdated REPLY component to change an attendee's participation status in the organizer's calendar, with the change applied automatically during message delivery. The vulnerability affects ZCS 10.1.16 and 10.1.21 through improper identity validation in the email calendar delivery pipeline.

Affected products

Zimbra Collaboration Suite 10.1.16, 10.1.21

Timeline

2026-10-23: disclosed

References

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