Vulnerability · Published Nov 27, 2025 · Assigned by Mattermost
CVE-2025-12421Account Takeover via Code Exchange Endpoint
Critical 9.9
In plain English
A critical-severity security flaw in Mattermost from Mattermost. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 39% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Mattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to to verify that the token used during the code exchange originates from the same authentication flow, which allows an authenticated user to perform account takeover via a specially crafted email address used when switching authentication methods and sending a request to the /users/login/sso/code-exchange endpoint. The vulnerability requires ExperimentalEnableAuthenticationTransfer to be enabled (default: enabled) and RequireEmailVerification to be disabled (default: disabled).
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/mattermost/mattermost-server | 10.11.5 | GHSA-mp6x-97xj-9x62 |
| Go | github.com/mattermost/mattermost-server | 11.0.3 | GHSA-mp6x-97xj-9x62 |
| Go | github.com/mattermost/mattermost-server | 10.12.2 | GHSA-mp6x-97xj-9x62 |
| Go | github.com/mattermost/mattermost-server | 10.5.13 | GHSA-mp6x-97xj-9x62 |
| Go | github.com/mattermost/mattermost-server | no fix listed | GO-2025-4170 |
| Go | github.com/mattermost/mattermost-server/v5 | no fix listed | GO-2025-4170 |
| Go | github.com/mattermost/mattermost-server/v6 | no fix listed | GO-2025-4170 |
| Go | github.com/mattermost/mattermost/server/v8 | 8.0.0-20251022210333-acda1fb5dd46 | GO-2025-4170 |
| Go | github.com/mattermost/mattermost/server/v8 | 8.0.0-20251022210333-acda1fb5dd46 | GHSA-mp6x-97xj-9x62 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mattermost | Mattermost | 11.0.0 – through 11.0.210.12.0 – through 10.12.110.11.0 – through 10.11.410.5.0 – through 10.5.12 |
Weakness: CWE-303 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H