Zimbra Collaboration Suite Calendar Processing Authentication Bypass via Forged iCalendar REQUEST Organizer Identity

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-93629
StatePUBLISHED
Assignerrapid7
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-23 14:17:56 UTC
Updated2026-10-23 16:44:17 UTC
DescriptionAn 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.

Risk And Classification

Primary CVSS: v3.1 5.3 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Problem Types: CWE-290 | CWE-290 CWE-290 Authentication bypass by spoofing

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
3.1CNACVSS5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Zimbra Zimbra Collaboration Suite affected 10.1.21 semver Not specified

References

ReferenceSourceLinkTags
www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1 [email protected] www.rapid7.com
wiki.zimbra.com/wiki/Zimbra_Security_Advisories [email protected] wiki.zimbra.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Jonah Burgess (CryptoCat), Senior Security Researcher, Rapid7 (en)

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