CVE-2026-6342 PUBLISHED

Group prefix matching bypass for subscriptions

Assigner: Mattermost
Reserved: 15.04.2026 Published: 18.05.2026 Updated: 18.05.2026

Mattermost Plugins versions <=11.5 11.1.5 10.13.11 11.3.4.0 fail to appropriately check for valid namespaces which allows plugin users to create subscriptions to groups that were not whitelisted via creating groups that share the same prefix as a whitelisted group. Mattermost Advisory ID: MMSA-2026-00601

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
CVSS Score: 4.3

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

CVSS 3.1

Product Status

Vendor	Mattermost
Product	Mattermost
Versions	Default: unaffected affected from 0 to 11.1.5 (incl.) affected from 0 to 10.13.11 (incl.) affected from 0 to 11.3.4 (incl.) Version 11.6.0 is unaffected Version 11.5.2 is unaffected Version 10.11.14 is unaffected Version 11.4.4 is unaffected

Solutions

Update Mattermost Plugins to versions 11.6.0, 11.5.2, 10.11.14, 11.4.4 or higher.

Credits

eahmed finder

References

MMSA-2026-00601

Problem Types

CWE-863: Incorrect Authorization CWE