What is CVE-2026-93629?

CVE-2026-93629 is a medium-severity vulnerability in Zimbra Collaboration Suite, classified under Authentication Bypass by Spoofing. CVSS score: 5.3/10. Published 2026-10-23.

How severe is CVE-2026-93629?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Vulnerability in Zimbra Collaboration Suite

CVE-2026-93629

An organizer authentication vulnerability in Zimbra Collaboration Suite (ZCS) allows an unauthenticated email sender to insert calendar invitations attributed to another user. The email delivery path permits external invitations but does not verify that the message sender is authorized to use the iCalendar ORGANIZER identity. When automatic invitation insertion is enabled, a crafted REQUEST component creates an event containing attacker-selected meeting details and reminders under a forged organizer without recipient interaction. No corresponding event is created in the claimed organizer's calendar. ZCS 10.1.16 and 10.1.21 are affected.

Published 2026-10-23 · last modified 2026-10-23.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Zimbra Collaboration Suite

Weakness classification (CWE)

CWE-290 — Authentication Bypass by Spoofing

References

wiki.zimbra.com/wiki/Zimbra_Security_Advisories (vendor-advisory)
www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/ (related)

Frequently asked questions

What is CVE-2026-93629?: CVE-2026-93629 is a medium-severity vulnerability in Zimbra Collaboration Suite, classified under Authentication Bypass by Spoofing. CVSS score: 5.3/10. Published 2026-10-23.
How severe is CVE-2026-93629?: Medium severity. CVSS v3 base score is 5.3 out of 10.