CVE-2026-93634

MEDIUM 4.3

Zimbra Collaboration Suite Cross-Account Authorization Bypass via Forged Shared-File Records

CVSS Score

4.3

EPSS Score

0.0%

EPSS Percentile

0th

A cross-account authorization vulnerability in Zimbra Collaboration Suite (ZCS) allows an authenticated user to insert forged shared-file records into another user's mailbox through FileSharedWithMeRequest. The request bypasses delegated-account authorization and accepts attacker-selected file metadata, owner identifiers and declared sizes without validating a corresponding document share. An attacker can plant entries attributed to another real local account without that account sharing a document. No victim interaction is required. ZCS 10.1.16 and 10.1.20 are affected.

CWE	CWE-639
Vendor	zimbra
Product	zimbra collaboration suite
Published	Oct 23, 2026

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CVSS v3 Breakdown

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

None

Affected Versions

Zimbra / Zimbra Collaboration Suite

0 ≤ 10.1.20

References

NVD ↗ CVE.org ↗ EPSS Data ↗

wiki.zimbra.com: https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories rapid7.com: https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/

Credits

Jonah Burgess (CryptoCat), Senior Security Researcher, Rapid7