---
id: "CVE-2026-93634"
kind: "vulnerability"
aliases: ["CVE-2026-93634"]
title: "Zimbra Collaboration: forged shared-file entries planted in other users' mailboxes"
severity: "medium"
cvss: 4.3
epss: 0.00295
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["mail", "package", "self-hosted", "zimbra"]
not_affected_if: ["managed-hosting"]
published_at: "2026-10-23T14:17:57+00:00"
first_seen_at: "2026-10-23T21:57:34+00:00"
updated_at: "2026-10-25T12:38:49+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-93634", "first_seen_at": "2026-10-23T21:57:34+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-93634", "first_seen_at": "2026-10-25T12:38:49+00:00"}]
---

# Zimbra Collaboration: forged shared-file entries planted in other users' mailboxes

Zimbra Collaboration Suite lets an authenticated user insert fake shared-file records into another local account's mailbox through the FileSharedWithMeRequest endpoint. The request skips delegated-account checks and does not verify that a share exists, so an attacker can plant entries that look like they came from a real user.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Confirm the Zimbra Collaboration version with `zmcontrol -v` on the mail server; versions 10.1.16 and 10.1.20 are listed as affected.
- unknown for other checks; the sources do not describe log entries or config flags to inspect.

## Fix

- Zimbra Collaboration: move to a fixed release from the vendor; the sources do not name the fixed version.
- unknown for interim mitigations; the sources do not say.

## Timeline

- 2026-10-23T21:57:34+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-93634
- 2026-10-25T12:38:49+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-93634

## From the sources

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.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_