CVE-2026-12284: Mattermost Desktop App Missing IPC Sender Validation in Calls Leave Handler

Severity: low (CVSS 3.7 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-17 · updated 2026-10-13
Weakness: CWE-346

Description

Mattermost Desktop App versions <=6.2 6.2.2.0 fails to validate the IPC sender in the leaveCall handler which allows a malicious or compromised Mattermost server (or a user with script access to a connected server view) to disconnect an active call belonging to a different connected server via the desktopAPI.leaveCall IPC message. Mattermost Advisory ID: MMSA-2026-00699

Affected products

Mattermost Desktop: from 6.2.0 before 6.2.3 — fixed in 6.2.3

How to fix

Upgrade to a fixed version: Mattermost Desktop 6.2.3. Check the vendor advisory for mitigations.

References

https://mattermost.com/security-updates

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