Skip to content
OpenAdvisories
Medium WID-SEC-2026-1705 3 CVEs

Mattermost Server und Plugins: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff

Published May 27, 2026 · Updated Jun 28, 2026 · Revision 2 · de-DE

Vendor: Mattermost Product: Mattermost Platform: Linux Platform: Windows

Summary

Ein Angreifer kann mehrere Schwachstellen in Mattermost Server und Plugins ausnutzen, um einen nicht näher spezifizierten Angriff durchzuführen.

Product

Mattermost ist ein webbasierter Instant-Messaging-Dienst.

Vulnerabilities 3

  • Medium 6.8
    CVE-2026-9699

    Mattermost Agents plugin logs unsanitized OpenAI API keys on authentication errors

    Mattermost Plugins versions <=11.6 10.18.11 11.3.6 11.6.5.0 fail to sanitize error responses from the OpenAI API before logging, which allows a user with access to server logs or support packets to obtain a valid or partially reconstructable OpenAI API key vi…

    Mattermost Mattermost
  • Medium 6.5
    CVE-2026-4339

    SSRF via unvalidated attachment URLs in Mattermost Agents plugin MCP server

    Mattermost versions 10.11.x <= 10.11.18, 11.6.x <= 11.6.3, 11.5.x <= 11.5.6 fail to validate attachment URLs against internal or private IP ranges in the Mattermost Agents plugin MCP server which allows an attacker with access to the MCP server in stdio mode …

    Mattermost Mattermost
  • Low 3.5
    CVE-2026-3472

    Markdown image rendering bypass in AI bot tool result posts in Mattermost

    Mattermost versions 10.11.x <= 10.11.18, 11.6.x <= 11.6.3, 11.5.x <= 11.5.6 fail to properly apply markdown image rendering restrictions to AI bot tool result posts, which allows an authenticated attacker to exfiltrate data to an attacker-controlled server vi…

    Mattermost Mattermost

Revision history

  1. #2

    Referenz(en) aufgenommen: CVE-2026-9699, GHSA-GR4W-63R3-8H38, CVE-2026-4339, EUVD-2026-39779, CVE-2026-3472, EUVD-2026-39775, EUVD-2026-39778

  2. #1

    Initiale Fassung

References