Zimbra Collaboration Suite Calendar Processing Authentication Bypass via Forged iCalendar REPLY Attendee Response (Zimbra Zimbra Collaboration Suite)
At a glance
- Source
- NVD
- EPSS
- EPSS 0.27 % · percentile 19 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- rapid7
- NVD status
- Undergoing Analysis
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 An attacker who knows the meeting UID, organizer address and attendee address can send a non-outdated reply that changes the attendee's participation status in the organizer's calendar.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.
Weaknesses (CWE)
- CWE-290 — Authentication Bypass by Spoofing
References
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | MEDIUM 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N | rapid7 |
| CVSS 3.1 | MEDIUM 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N | NVD · cve@rapid7.com (Secondary) |
European references
- ENISA EUVD · EUVD-2026-108964
- GCVE · GCVE-0-2026-93628
Affected products
| Product | Versions |
|---|---|
| Zimbra · Zimbra Collaboration Suite | affected 0 ≤ 10.1.21 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |