CVE-2025-12419: Mattermost fails to properly validate OAuth state tokens during OpenID Connect authentication

CVE-2025-12419 · Severity: critical · CVSS 9.9 · Published 2025-11-27

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.

Technologies: github.com/mattermost/mattermost-server (Go), github.com/mattermost/mattermost-server/v5 (Go), github.com/mattermost/mattermost-server/v6 (Go), github.com/mattermost/mattermost/server/v8 (Go), Mattermost Server. Vendors: Go, Mattermost.

Quick answers

Is CVE-2025-12419 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2025-12419 being exploited in the wild.
How severe is CVE-2025-12419?
Critical severity, with a CVSS score of 9.9, published 27 November 2025.
Which products and versions are affected?
github.com/mattermost/mattermost-server (Go) SEMVER:introduced=0, SEMVER:introduced=10.12.0,fixed=10.12.2; github.com/mattermost/mattermost-server/v5 (Go) SEMVER:introduced=0; github.com/mattermost/mattermost-server/v6 (Go) SEMVER:introduced=0; github.com/mattermost/mattermost/server/v8 (Go) SEMVER:introduced=0,fixed=8.0.0-20251028000919-d3ed703dc833.
Is there a fix for CVE-2025-12419?
Yes. github.com/mattermost/mattermost-server (Go): upgrade to 10.12.2 or later; github.com/mattermost/mattermost/server/v8 (Go): upgrade to 8.0.0-20251028000919-d3ed703dc833 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2025-12419?
Check whether you run github.com/mattermost/mattermost-server (Go), github.com/mattermost/mattermost-server/v5 (Go), github.com/mattermost/mattermost-server/v6 (Go) or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • github.com/mattermost/mattermost-server (Go): upgrade to 10.12.2 or later
    go get github.com/mattermost/mattermost-server@v10.12.2
  • github.com/mattermost/mattermost/server/v8 (Go): upgrade to 8.0.0-20251028000919-d3ed703dc833 or later
    go get github.com/mattermost/mattermost/server/v8@v8.0.0-20251028000919-d3ed703dc833

Affected products

  • github.com/mattermost/mattermost-server (Go) SEMVER:introduced=0, SEMVER:introduced=10.12.0,fixed=10.12.2
  • github.com/mattermost/mattermost-server/v5 (Go) SEMVER:introduced=0
  • github.com/mattermost/mattermost-server/v6 (Go) SEMVER:introduced=0
  • github.com/mattermost/mattermost/server/v8 (Go) SEMVER:introduced=0,fixed=8.0.0-20251028000919-d3ed703dc833
  • Mattermost Server

Identifiers

  • CVE-2025-12419
  • GHSA-3x39-62h4-f8j6
  • GO-2025-4168

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