CVE-2025-31363: Mattermost Server

Medium severity, CVSS 6.5. EPSS: 0.3% chance of exploitation in the next 30 days.

Mattermost versions 10.4.x <= 10.4.2, 10.5.x <= 10.5.0, 9.11.x <= 9.11.9 fail to restrict domains the LLM can request to contact upstream which allows an authenticated user to exfiltrate data from an arbitrary server accessible to the victim via performing a prompt injection in the AI plugin's Jira tool.

Affected products

• Mattermost Mattermost Server: from 9.11.0, before 9.11.10 (fixed in 9.11.10); from 10.4.0, before 10.4.3 (fixed in 10.4.3); version 10.5.0 only

Published 2025-04-16. Last modified 2026-06-17.