---
id: CVE-2026-115786
title: >-
  Zimbra Collaboration Suite Shared-File Mailbox Quota Accounting Error Enables
  Quota Exhaustion
summary: >-
  A mailbox quota-accounting vulnerability in Zimbra Collaboration Suite (ZCS)
  allows an authenticated user to consume another user’s mailbox quota by
  repeatedly sharing and revoking a document. Creation of the recipient’s
  shared-file reco…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
cvssSource: cna
cwe:
  - CWE-682
vendor: Zimbra
product: Zimbra Collaboration Suite
affected:
  - collaboration_suite <= 10.1.20
published: '2026-10-23'
updated: '2026-10-23'
sourceUpdated: '2026-10-23T13:53:33.918Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-115786'
references:
  - url: 'https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories'
  - url: >-
      https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/
tags:
  - cve.org
ingestedAt: '2026-10-23T14:28:08.698Z'
---

## Overview

A mailbox quota-accounting vulnerability in Zimbra Collaboration Suite (ZCS) allows an authenticated user to consume another user’s mailbox quota by repeatedly sharing and revoking a document. Creation of the recipient’s shared-file record charges the document size to mailbox-wide usage. Revocation deletes the record and reverses its folder counters without reversing the mailbox-wide charge. Repeated normal share notifications therefore accumulate quota usage after the visible records are gone. On accounts with a finite quota, this can prevent incoming mail and other size-increasing operations without recipient interaction. The issue affects ZCS 10.1.16 and 10.1.20.

## Affected

- `collaboration_suite <= 10.1.20`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.