---
id: CVE-2026-50053
title: >-
  Zimbra Collaboration Suite RestFilter Request Attribute Override via
  Unauthenticated URL Parameters
summary: >-
  A request attribute override vulnerability in Zimbra Collaboration Suite (ZCS)
  allows unauthenticated requests to /h/* to populate servlet attributes
  intended for trusted internal dispatch. RestFilter copies URL parameters
  specifying an …
severity: high
cvss: 8.7
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N'
cvssSource: cna
cwe:
  - CWE-642
vendor: Zimbra
product: Zimbra Collaboration Suite
affected:
  - collaboration_suite <= 10.1.17
published: '2026-10-23'
updated: '2026-10-23'
sourceUpdated: '2026-10-23T13:38:40.748Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-50053'
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: '2026-10-23T14:28:08.704Z'
---

## Overview

A request attribute override vulnerability in Zimbra Collaboration Suite (ZCS) allows unauthenticated requests to /h/* to populate servlet attributes intended for trusted internal dispatch. RestFilter copies URL parameters specifying an authentication token, target account, target item and dispatch state into the request attributes consumed by the Classic Web Client. Combined with CVE-2026-10632 on ZCS 10.1.16, this allows an attacker to supply their own valid token and document identifiers and execute JavaScript in another user's signed-in browser session. ZCS 10.1.17 blocks that XSS chain by changing the document renderer, but retains the request attribute override.

## Affected

- `collaboration_suite <= 10.1.17`

## Remediation

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