CVE-2025-12421 — Incorrect Implementation of Authentication Algorithm in Mattermost Mattermost-server

CWE-303 — Incorrect Implementation of Authentication AlgorithmCWE-287 — Improper Authentication5 documents4 sources
Severity
9.9CRITICALNVD
EPSS
0.1%
top 70.45%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
4
Github.com Mattermost Mattermost-serverGithub.com Mattermost Mattermost Server V8Mattermost Server+1 more
Timeline
PublishedNov 27
Latest updateDec 15

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…

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:HExploitability: 3.1 | Impact: 6.0

Affected Packages4 packages

▶NVDmattermost/mattermost_server10.5.0 — 10.5.13+3
▶Gogithub.com/mattermost_mattermost_server_v8< 8.0.0-20251022210333-acda1fb5dd46
▶CVEListV5mattermost/mattermost11.0.0 — 11.0.2+3

🔴Vulnerability Details

4
OSV
Mattermost fails to to verify the token used during code exchange in github.com/mattermost/mattermost-server↗2025-12-15
▶
CVEList
Account Takeover via Code Exchange Endpoint↗2025-11-27
▶
GHSA
Mattermost fails to to verify the token used during code exchange↗2025-11-27
▶
OSV
Mattermost fails to to verify the token used during code exchange↗2025-11-27
▶
CVE-2025-12421 — CRITICAL severity | cvebase