DoS via URL Previews Rendering Malicious SVGs

Summary

Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to prevent rendering of external SVGs on link embeds which allows unauthenticated users to crash the Mattermost webapp and desktop app via creating an issue or PR on GitHub.. Mattermost Advisory ID: MMSA-2026-00595

Timeline

1. Mar 25, 2026, 4:30 PM UTCCVE published
2. Mar 26, 2026, 5:11 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Mar 26, 2026, 5:11 PM UTCRecord last updated

Affected versions

• Mattermost Mattermost

  From 11.4.0 · through 11.4.0; From 11.3.0 · through 11.3.1; From 11.2.0 · through 11.2.3; From 10.11.0 · through 10.11.11

• github.com/mattermost/mattermost-serverGo

  From 10.11.0-rc1+incompatible · fixed in 10.11.2+incompatible; From 11.2.0-rc1+incompatible · fixed in 11.2.4+incompatible; From 11.3.0-rc1+incompatible · fixed in 11.3.2+incompatible; From 11.4.0-rc1+incompatible · fixed in 11.4.1+incompatible

• github.com/mattermost/mattermost-server/v5Go

  All versions

• github.com/mattermost/mattermost-server/v6Go

  All versions

• github.com/mattermost/mattermost/server/v8Go

  From 8.0.0-20260105080200-d27a2195068d · fixed in 8.0.0-20260217110922-b7d4a1f1f59b

• github.com/mattermost/mattermost/server/v8Go

  From 11.4.0-rc1 · fixed in 11.4.1

• github.com/mattermost/mattermost/server/v8Go

  From 11.3.0-rc1 · fixed in 11.3.2

• github.com/mattermost/mattermost/server/v8Go

  From 11.2.0-rc1 · fixed in 11.2.4

• github.com/mattermost/mattermost/server/v8Go

  From 10.11.0-rc1 · fixed in 10.11.2

References 1