CVE-2025-12421

Account Takeover via Code Exchange Endpoint

Published: Nov 27, 2025Updated: Dec 3, 2025 Sources: CVE List NVD GHSA BDUCWE-303

9.9CRITICAL

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).

No summary for this CVE yet.

CVSS Vector Breakdown

Exploitability

AV:NAttack Vector

Network

AC:LAttack Complexity

Low

PR:LPrivileges Required

Low

UI:NUser Interaction

None

Scope

S:CScope

Changed

Impact

C:HConfidentiality

High

I:HIntegrity

High

A:HAvailability

High

Open in CVSS calculator →

Weaknesses

CWE-303

Affected Products

Mattermost

commercial·US

mattermost serverOn-premWeb App

Communications / messaging-chat

MattermostOn-premWeb App

Communications / messaging-chat

package-ecosystem

github.com/mattermost/mattermost/server/v8

OSS Libraries

github.com/mattermost/mattermost-server

OSS Libraries

Mattermost Inc

commercial·USaka mattermost

MattermostOn-premWeb App

Communications / messaging-chat

Exploitability

Official Patch Available

Is your org exposed to CVE-2025-12421?Request an assessment to establish which checks are appropriate for your systems. Check my exposure

References

https://mattermost.com/security-updates

mattermost.com

https://nvd.nist.gov/vuln/detail/CVE-2025-12421

nvd.nist.gov

https://github.com/mattermost/mattermost/commit/5072bbf689a46b3b97b2373f26149f5891396e6b

github.com

and 4 more references View all →

Unlock Complete Vulnerability Intelligence

Get the full picture for CVE-2025-12421 and every CVE in our database. Create a free account — no credit card required.

Create Free Account

Plain-language analysis

Impact assessment and exploitation scenario in plain English

Attack graph visualization

Interactive attack path and kill chain mapping

Exploit details & PoC links

ExploitDB, Metasploit, GitHub PoCs with direct links

Nuclei scanner templates

Ready-to-use vulnerability scanner templates

Full remediation guide

Patch instructions, workarounds, and compliance impact

Interactive AI chat

Ask questions about this vulnerability in natural language

Related vulnerabilities

Semantically similar CVEs and attack patterns

REST API & MCP access

Integrate vulnerability data into your workflows