CVE-2026-93628 Zimbra Collaboration Suite Calendar Processing Authentication Bypass via Forged iCalendar REPLY Attendee Response
- Exploited in the wild
- Not known
- Fix
- None listed
What is CVE-2026-93628?
CVE-2026-93628 is a medium-severity vulnerability in Zimbra Collaboration Suite, published on 23 Oct 2026.
Official description
An attendee authentication vulnerability in the email calendar processing of Zimbra Collaboration Suite (ZCS) allows an unauthenticated sender to forge another attendee's response to an existing meeting. Zimbra passes a null sender identity when processing iCalendar REPLY components, causing the attendee authorization filter to be skipped. An attacker who knows the meeting UID, organizer address and attendee address can send a non-outdated reply that changes the attendee's participation status in the organizer's calendar. The change occurs automatically during delivery without organizer or attendee interaction. ZCS 10.1.16 and 10.1.21 are affected.
Weakness: CWE-290
Which versions are affected by CVE-2026-93628?
How do I fix CVE-2026-93628?
No fix has been published for CVE-2026-93628 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-93628 being exploited?
There is no known exploitation of CVE-2026-93628 in the wild and no public exploit code.
Sources
Also known as GHSA-p5gv-qg22-w4gq.