Mattermost 11.x account switch fails to reject OAuth sessions SSO takeover
CVE-2026-19076 Published on October 16, 2026

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

Vendor Advisory NVD

Vulnerability Analysis

CVE-2026-19076 is exploitable with network access, and requires user privileges. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality, a high impact on integrity, and no impact on availability.

Attack Vector:
NETWORK
Attack Complexity:
HIGH
Privileges Required:
HIGH
User Interaction:
NONE
Scope:
UNCHANGED
Confidentiality Impact:
NONE
Integrity Impact:
HIGH
Availability Impact:
NONE

Weakness Type

What is an AuthZ Vulnerability?

The software performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. This allows attackers to bypass intended access restrictions.

CVE-2026-19076 has been classified to as an AuthZ vulnerability or weakness.


Products Associated with CVE-2026-19076

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MatterMost
 

Affected Versions

Mattermost: