CVE-2026-93634 Zimbra Collaboration Suite Cross-Account Authorization Bypass via Forged Shared-File Records

What is CVE-2026-93634?

CVE-2026-93634 is a medium-severity vulnerability in Synacor Zimbra Collaboration Suite, published on 23 Oct 2026.

Official description

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.

Weakness: CWE-639

Which versions are affected by CVE-2026-93634?

It affects 1 product.

Products include Synacor Zimbra Collaboration Suite.

How do I fix CVE-2026-93634?

No fix has been published for CVE-2026-93634 yet. Limit exposure of the affected software until one is available.

Is CVE-2026-93634 being exploited?

There is no known exploitation of CVE-2026-93634 in the wild and no public exploit code.

Other vulnerabilities in Synacor Zimbra Collaboration Suite

• CVE-2024-45519 Synacor Zimbra Collaboration Suite (ZCS) Command Execution Exploited Critical 10.0
• CVE-2022-41352 Synacor Zimbra Collaboration Suite (ZCS) Arbitrary File Upload Exploited Critical 9.8
• CVE-2022-37042 Synacor Zimbra Collaboration Suite (ZCS) Authentication Bypass Exploited Critical 9.8
• CVE-2022-27924 Synacor Zimbra Collaboration Suite (ZCS) Command Injection Exploited Critical 9.8
• CVE-2020-7796 Synacor Zimbra Collaboration Suite (ZCS) Server-Side Request Forgery Exploited Critical 9.8

All Synacor Zimbra Collaboration Suite vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-8563-28f8-ph7v.