---
id: CVE-2026-66911
title: Stored Cross-Site Scripting in Zimbra
summary: >-
  Zimbra is vulnerable to stored cross-site scripting (XSS) via the
  Content-Location MIME header in email attachments. Due to lack of sanitization
  of the Content-Location header, an attacker can set it to a javascript: URI.
  An unauthentica…
severity: medium
cvss: 5.3
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N'
cvssSource: cna
cwe:
  - CWE-79
vendor: Synacor
product: Zimbra Collaboration
affected:
  - zimbra_collaboration < 10.1.21
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-05T21:19:04.494780Z'
published: '2026-10-29'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T21:19:23.873Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-66911'
references:
  - url: 'https://cert.pl/en/posts/2026/10/CVE-2026-66911'
  - url: 'https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories'
tags:
  - cve.org
epss: 0.0054
epssPercentile: 0.45639
ingestedAt: '2026-11-01T20:00:16.961Z'
---

## Overview

Zimbra is vulnerable to stored cross-site scripting (XSS) via the Content-Location MIME header in email attachments. Due to lack of sanitization of the Content-Location header, an attacker can set it to a javascript: URI. An unauthenticated remote attacker can send a crafted email to a victim; when the victim opens the email in the Zimbra web interface and clicks the attachment name, the JavaScript payload executes in the victim's browser context. This issue was fixed in version 10.1.21

## Affected

- `zimbra_collaboration < 10.1.21`

## Remediation

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