CVE-2026-9597 PUBLISHED

Deactivated guest accounts can authenticate via magic-link token in Mattermost REST API login endpoint

Assigner: Mattermost
Reserved: 26.05.2026 Published: 13.07.2026 Updated: 13.07.2026

Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4 fail to verify whether a guest account is deactivated before creating a session in the magic-link token login path, which allows a deactivated guest user to obtain a fully functional session via a magic-link token issued prior to deactivation.. Mattermost Advisory ID: MMSA-2026-00681

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
CVSS Score: 5.4

Attack Vector	Network	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	Low
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 11.7.0 to 11.7.2 (incl.) affected from 11.6.0 to 11.6.4 (incl.) Version 11.8.0 is unaffected Version 11.7.3 is unaffected Version 11.6.5 is unaffected

Solutions

Update Mattermost to versions 11.8.0, 11.7.3, 11.6.5 or higher.

Credits

alimursaliyev finder

References

MMSA-2026-00681

Problem Types

CWE-305 – Authentication Bypass by Primary Weakness CWE