CVE-2026-19076

EUVD-2026-102747

16.10.2026, 08:17

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

Provider	Type	Base Score	Atk. Vector	Atk. Complexity	Priv. Required	Vector
Mattermost	CNA	4.4 MEDIUM	NETWORK	HIGH	HIGH	CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:H/A:N

Base Score

CVSS 3.x

EPSS Score

Percentile: 8.97%

Early Detection

Affected products identified ahead of NVD analysis through intelligence sources.

Vendor	Product	Version	Source
mattermost	mattermost	𝑥 ≤ 11.10.0	CNA
mattermost	mattermost	11.7.0 ≤ 𝑥 ≤ 11.7.9	CNA
mattermost	mattermost	11.9.0 ≤ 𝑥 ≤ 11.9.1	CNA
mattermost	mattermost	11.8.0 ≤ 𝑥 ≤ 11.8.5	CNA

Common Weakness Enumeration

CWE-863 - Incorrect Authorization
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.

References

https://mattermost.com/security-updates