---
id: CVE-2026-75588
title: >-
  Mattermost Desktop App versions <=6.2 6.2.2.0 fail to validate the URL scheme
  when checking whether a target URL is internal to the connected server, which
  allows a network-positioned attacker to load a plugin popout window over an
  insec…
summary: >-
  Mattermost Desktop App versions <=6.2 6.2.2.0 fail to validate the URL scheme
  when checking whether a target URL is internal to the connected server, which
  allows a network-positioned attacker to load a plugin popout window over an
  insec…
severity: low
cvss: 2.6
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:L/A:N'
cwe:
  - CWE-1287
vendor: Mattermost
product: Mattermost
affected:
  - Mattermost <= 6.2.2
published: '2026-09-17'
updated: '2026-09-18'
sourceUpdated: '2026-09-18T13:46:33.503'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-75588'
references:
  - url: 'https://mattermost.com/security-updates'
    label: responsibledisclosure@mattermost.com
tags:
  - nvd
  - cve.org
epss: 0.00167
epssPercentile: 0.06334
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-17T19:21:58.878556Z'
ingestedAt: '2026-09-17T16:21:47.709Z'
---

## Overview

Mattermost Desktop App versions <=6.2 6.2.2.0 fail to validate the URL scheme when checking whether a target URL is internal to the connected server, which allows a network-positioned attacker to load a plugin popout window over an insecure connection via a link using a downgraded URL scheme. Mattermost Advisory ID: MMSA-2026-00717

## Remediation

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