CVE-2026-12284 PUBLISHED

Mattermost Desktop App Missing IPC Sender Validation in Calls Leave Handler

Assigner: Mattermost
Reserved: 15.06.2026 Published: 17.09.2026 Updated: 17.09.2026

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

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
CVSS Score: 3.8

Attack Vector	Network	Scope	Unchanged
Attack Complexity	High	Confidentiality Impact	None
Privileges Required	None	Integrity Impact	None
User Interaction	None	Availability Impact	Low

CVSS 3.1

Product Status

Vendor	Mattermost
Product	Mattermost
Versions	Default: unaffected affected from 0 to 6.2.2 (incl.) Version 6.3.0 is unaffected Version 6.2.3.0 is unaffected

Solutions

Update Mattermost Desktop App to versions 6.3.0, 6.2.3.0 or higher.

Credits

Juho Forsén finder

References

MMSA-2026-00699

Problem Types

CWE-346: Origin Validation Error CWE