CVE-2026-93629
MEDIUM 5.3An 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.
No known exploitation, public exploit, or elevated probability at this time. Track for changes.
Exploitation likelihood
0.3%chance of exploitation in 30 days · 19th percentile
Impact if exploited
5.3CVSS 3.1 · MEDIUM
- ConfidentialityNone
- IntegrityLow
- AvailabilityNone
What an attacker needs
- ✓Access: Reachable over the network — no local access needed
- ✓Privileges: No account or privileges required
- ✓User interaction: No user interaction needed
- ✓Complexity: No special conditions — reliably repeatable
✓ lowers the bar for an attacker · ⚠ raises it
Proof of concept
No public PoC is currently catalogued.
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Data snapshot:
Weakness (CWE)
- CWE-290: Authentication bypass by spoofing
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
References and research data (JSON)
All CVSS metrics
- MEDIUM 5.3 v3.1 · CNA Primary
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N - MEDIUM 5.3 v3.1 · NVD Secondary
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
References
Advisories
- https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories CVE record · rapid7 · Updated 2026-10-23T13:19:26.405Z
NVD · CVE-2026-93629 · Updated 2026-10-23T16:44:17.950 - https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-108965 EUVD · EUVD-2026-108965
Technical & other
- https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/ CVE record · rapid7 · Updated 2026-10-23T13:19:26.405Z
NVD · CVE-2026-93629 · Updated 2026-10-23T16:44:17.950