CVE-2026-27769 PUBLISHED

Connected Workspaces: Malicious remote server can manipulate arbitrary user's status

Assigner: Mattermost
Reserved: 16.03.2026 Published: 15.04.2026 Updated: 15.04.2026

Mattermost versions 10.11.x <= 10.11.12 fail to validate whether users were correctly owned by the correct Connected Workspace which allows a malicious remote server connected using the Conntexted Workspaces feature to change the displayed status of local users via the Connected Workspaces API.. Mattermost Advisory ID: MMSA-2026-00603

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:N
CVSS Score: 2.7

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

CVSS 3.1

Product Status

Vendor	Mattermost
Product	Mattermost
Versions	Default: unaffected affected from 10.11.0 to 10.11.12 (incl.) Version 11.5.0 is unaffected Version 10.11.13 is unaffected

Solutions

Update Mattermost to versions 11.5.0, 10.11.13 or higher.

Credits

daw10 finder

References

MMSA-2026-00603

Problem Types

CWE-862: Missing Authorization CWE