CVE-2026-93628 (GCVE-0-2026-93628)

Vulnerability from cvelistv5 – Published: 2026-10-23 13:18 – Updated: 2026-10-28 20:02
VLAI
Title
Zimbra Collaboration Suite Calendar Processing Authentication Bypass via Forged iCalendar REPLY Attendee Response
Summary
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 An attacker who knows the meeting UID, organizer address and attendee address can send a non-outdated reply that changes the attendee's participation status in the organizer's calendar.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.
Severity
5.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-28 18:23 UTC
CWE
  • CWE-290 - Authentication bypass by spoofing
Assigner
rapid7 CNA under the mitre root
CNA scorecard B 76/100 over 81 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Zimbra Zimbra Collaboration Suite Affected: 0 , ≤ 10.1.21 (semver)
guessed Create a notification for this product.
Date Public
2026-10-23 12:46
Credits
Jonah Burgess (CryptoCat), Senior Security Researcher, Rapid7
Show details on NVD website
To clipboard 

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