CVE-2025-12419

Account takeover on OAuth/OpenID-enabled servers

State: Published
Severity: 9.9 Critical
Published: Nov 27, 2025
Updated: Feb 26, 2026
Reserved: Oct 28, 2025

Description

Mattermost versions 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12, 11.0.x <= 11.0.3 fail to properly validate OAuth state tokens during OpenID Connect authentication which allows an authenticated attacker with team creation privileges to take over a user account via manipulation of authentication data during the OAuth completion flow. This requires email verification to be disabled (default: disabled), OAuth/OpenID Connect to be enabled, and the attacker to control two users in the SSO system with one of them never having logged into Mattermost.

Scores

CVSS	Score	Vector	Source
3.1	9.9 Critical	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H	Mattermost

Weaknesses

CWE-303 Incorrect Implementation of Authentication Algorithm

Affected Products

Product	Versions
MattermostMattermost	10.12.0 through 10.12.1Affected 10.11.0 through 10.11.4Affected 10.5.0 through 10.5.12Affected 11.0.0 through 11.0.3Affected 11.1.0Not affected 10.12.2Not affected 10.11.5Not affected 10.5.13Not affected 11.0.4Not affected

References

https://mattermost.com/security-updates

Every record here comes from the CVE Program’s CVE List. © 1999–2026 The MITRE Corporation. CVE is a registered trademark of The MITRE Corporation. The records are reproduced under the CVE Program terms of use.