CVE-2026-16044 PUBLISHED

Insufficient validation of guest board admin privileges on archive import

Assigner: Mattermost
Reserved: 17.07.2026 Published: 17.08.2026 Updated: 17.08.2026

Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21 fail to prevent guest users from receiving Board Admin privileges during board archive import which allows a board member to escalate a guest user to Board Admin via importing a crafted .boardarchive file. Mattermost Advisory ID: MMSA-2026-00672

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
CVSS Score: 3.9

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

CVSS 3.1

Product Status

Vendor	Mattermost
Product	Mattermost
Versions	Default: unaffected affected from 11.7.0 to 11.7.6 (incl.) affected from 10.11.0 to 10.11.21 (incl.) Version 11.9.0 is unaffected Version 11.7.7 is unaffected Version 10.11.22 is unaffected

Solutions

Update Mattermost to versions 11.9.0, 11.7.7, 10.11.22 or higher.

Credits

ilent0 finder

References

MMSA-2026-00672

Problem Types

CWE-863: Incorrect Authorization CWE