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

Description

An 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.

Scores

EPSS (exploitation in 30 days)

0.27% · top 81% of all CVEs (6 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: yes · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.3.

Weakness

• CWE-290 Authentication bypass by spoofing (opens in a new tab)All about CWE-290 and its CVEs

Affected products

• Zimbra · Zimbra Collaboration Suite

  • affected ≤ 10.1.21

References (2)

• https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories (opens in a new tab)vendor-advisory
• https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/ (opens in a new tab)related

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-93629](https://trackcve.app/badge/CVE-2026-93629.svg)](https://trackcve.app/cve/CVE-2026-93629)

Record last updated 28 Oct 2026, 19:51 UTC.