CVE-2025-12421

CRITICAL
2025-11-27 [email protected]
9.9
CVSS 3.1
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CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

3
Patch Released
Mar 31, 2026 - 21:13 nvd
Patch available
Analysis Generated
Mar 28, 2026 - 19:24 vuln.today
CVE Published
Nov 27, 2025 - 18:15 nvd
CRITICAL 9.9

Tags

Information Disclosure Microsoft Mattermost Server Suse

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).

Analysis

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. Rated critical severity (CVSS 9.9), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.

Technical Context

This vulnerability is classified under CWE-303. 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 products include: Mattermost Mattermost Server.

Affected Products

Mattermost Mattermost Server.

Remediation

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

Priority Score

50
Low Medium High Critical
KEV: 0
EPSS: +0.1
CVSS: +50
POC: 0

Vendor Status

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CVE-2025-12421 vulnerability details – vuln.today
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