CVE-2026-75588

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

  • Published Sep 17, 2026
  • CVSS 2.6 low
  • 0.2% chance of exploitation in the next 30 days (EPSS)

Affected software

CVE-2026-75588 at the National Vulnerability Database