CVE-2026-93628
Zimbra Collaboration Suite Calendar Processing Authentication Bypass via Forged iCalendar REPLY Attendee Response
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CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Attack conditions and impact
Derived from the CNA (via NVD) CVSS 3.1 vectorThis vulnerability may be exploitable over the internet without authentication or user interaction.
| Metric | Value | Meaning |
|---|---|---|
| Attack vector AV | N | Network |
| Attack complexity AC | L | Low (easy) |
| Privileges required PR | N | None |
| User interaction UI | N | None |
| Scope S | U | Unchanged |
| Confidentiality C | N | None |
| Integrity I | L | Low |
| Availability A | N | None |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
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 An attacker who knows the meeting UID, organizer address and attendee address can send a non-outdated reply that changes the attendee's participation status in the organizer's calendar.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.
CVSS assessments
| Provider | Version | Score | Vector |
|---|---|---|---|
| NVD / [email protected] (Secondary) | 3.1 | 5.3 MEDIUM | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N |
| CNA / rapid7 | 3.1 | 5.3 MEDIUM | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N |
Affected products and packages
CNA (CVE.org)
| Vendor | Product | Versions |
|---|---|---|
| Zimbra | Zimbra Collaboration Suite | affected: 0 … <= 10.1.21 default: unaffected |
Linux distribution status
References (2)
- https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories NVD, CNA vendor-advisory
- https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/ NVD, CNA related