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Open-source package vulnerability · Go

CVE-2025-12421: Mattermost fails to to verify the token used during code exchange

criticalCVSS 3.1 9.9GHSA-mp6x-97xj-9x62

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.

Published Nov 27, 2025 · Updated Dec 1, 2025

Affected packages

github.com/mattermost/mattermost/server/v8

Ecosystem
Go
Affected
< 8.0.0-20251022210333-acda1fb5dd46
Fixed in
8.0.0-20251022210333-acda1fb5dd46
Check
go list -m github.com/mattermost/mattermost/server/v8

github.com/mattermost/mattermost-server

Ecosystem
Go
Affected
>= 11.0.0, < 11.0.3
Fixed in
11.0.3
Check
go list -m github.com/mattermost/mattermost-server

github.com/mattermost/mattermost-server

Ecosystem
Go
Affected
>= 10.12.0, < 10.12.2
Fixed in
10.12.2
Check
go list -m github.com/mattermost/mattermost-server

github.com/mattermost/mattermost-server

Ecosystem
Go
Affected
>= 10.11.0, < 10.11.5
Fixed in
10.11.5
Check
go list -m github.com/mattermost/mattermost-server

github.com/mattermost/mattermost-server

Ecosystem
Go
Affected
>= 10.5.0, < 10.5.13
Fixed in
10.5.13
Check
go list -m github.com/mattermost/mattermost-server

Advisory details

From the GitHub Advisory Database (CC BY 4.0).

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).

References

How this page is made: the data panel comes from the GitHub Advisory Database, CISA’s KEV catalog, the NVD and FIRST EPSS, and updates twice a day. No analysis has been written for this entry yet. Methodology

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