CVE-2025-12419

CRITICAL

Mattermost fails to properly validate OAuth state tokens during OpenID Connect authentication

Published November 27, 2025Updated December 17, 2025Source: osv

Summary

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.

Remediation

Upgrade to the fixed version using your package manager.

Update github.com/mattermost/mattermost-server to 11.0.4 or later

go get github.com/mattermost/mattermost-server@v11.0.4

Update github.com/mattermost/mattermost-server to 10.12.2 or later

go get github.com/mattermost/mattermost-server@v10.12.2

Update github.com/mattermost/mattermost-server to 10.11.5 or later

go get github.com/mattermost/mattermost-server@v10.11.5

Update github.com/mattermost/mattermost-server to 10.5.13 or later

go get github.com/mattermost/mattermost-server@v10.5.13

Update github.com/mattermost/mattermost/server/v8 to 8.0.0-20251028000919-d3ed703dc833 or later

go get github.com/mattermost/mattermost/server/v8@v8.0.0-20251028000919-d3ed703dc833

After upgrading, run your dependency scanner again to confirm the vulnerability is resolved.

Affected Packages (5)

Package	Ecosystem	Affected	Fixed In
github.com/mattermost/mattermost-server	go	All versions	11.0.4
github.com/mattermost/mattermost-server	go	All versions	10.12.2
github.com/mattermost/mattermost-server	go	All versions	10.11.5
github.com/mattermost/mattermost-server	go	All versions	10.5.13
github.com/mattermost/mattermost/server/v8	go	All versions	8.0.0-20251028000919-d3ed703dc833

Vulnerability Classification

Common Weakness Enumeration (CWE) identifiers for this vulnerability type.

CWE-287
Improper AuthenticationMITRE
CWE-303
View on MITRE

CVSS Score Breakdown

What the CVSS (Common Vulnerability Scoring System) 9.9 score means for each attack dimension.

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

References

Frequently Asked Questions

What is CVE-2025-12419?: Mattermost fails to properly validate OAuth state tokens during OpenID Connect authentication This vulnerability has been assigned a severity rating of CRITICAL (CVSS score: 9.9/10).
How do I check if my project is affected by CVE-2025-12419?: CVE-2025-12419 affects github.com/mattermost/mattermost-server and github.com/mattermost/mattermost/server/v8. Use GeekWala's free vulnerability scanner to check your dependencies against CVE-2025-12419 and 200,000+ other known vulnerabilities.

Severity & Exploitability

CVSS Score

9.9

Exploitation is straightforward and causes maximum impact. Patch immediately.

Also Known As

GHSA-3x39-62h4-f8j6

GO-2025-4168

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