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CVE-2026-93628

medium

An attendee authentication vulnerability in the email calendar processing of Zimbra Collaboration Suite (ZCS) allows an unauthenticated sender to forge another…

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 An attacker who knows the meeting UID, organizer address and attendee address can send a non-outdated reply that changes the attendee's participation status in the organizer's calendar.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
5.3
5.3 (CVSS v3.1)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Severity source: NVD CVSS v3.1 (cve@rapid7.com)
Timeline (UTC)
Published: 2026-10-23 14:17
Modified: 2026-10-28 20:18
NVD status: Undergoing Analysis
Last synced 15 hours ago
Verified against the source API 2026-10-28 20:34 UTC
Exploitation
Not listed in CISA KEV (as of last catalog sync)
Absence from KEV does not mean a CVE is not exploited. Exploitation status: unknown (no authoritative evidence in our sources).

Affected products

Not reported by the source (unknown — not "none").

Weakness classification (CWE)

CWE-290

Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.

Mitigation & advisories

No vendor advisory or patch reference tagged by NVD. Check the references below.

References

Data sources

NVD CVE API 2.0 — fetched 2026-10-28 20:34 UTC · record ↗

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