CVE-2026-19076 PUBLISHED

Mattermost fails to reject OAuth application sessions in account type switch, allowing account takeover via bearer token

Assigner: Mattermost
Reserved: 06.08.2026 Published: 16.10.2026 Updated: 16.10.2026

Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to reject OAuth application sessions in the account type switch endpoint, which allows an attacker with a valid OAuth bearer token for a target user to permanently take over that user's SSO-backed account by setting an attacker-controlled password and detaching the account from its identity provider via a crafted request to POST /api/v4/users/login/switch.. Mattermost Advisory ID: MMSA-2026-00758

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:H/A:N
CVSS Score: 4.4

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

CVSS 3.1

Product Status

Vendor	Mattermost
Product	Mattermost
Versions	Default: unaffected affected from 11.10.0 to 11.10.0 (incl.) affected from 11.7.0 to 11.7.9 (incl.) affected from 11.9.0 to 11.9.1 (incl.) affected from 11.8.0 to 11.8.5 (incl.) Version 11.11.0 is unaffected Version 11.10.1 is unaffected Version 11.7.10 is unaffected Version 11.9.2 is unaffected Version 11.8.6 is unaffected

Solutions

Update Mattermost to versions 11.11.0, 11.10.1, 11.7.10, 11.9.2, 11.8.6 or higher.

Credits

CERT PL finder

References

MMSA-2026-00758

Problem Types

CWE-863: Incorrect Authorization CWE