Mattermost versions 10.11.x <= 10.11.12, 11.5.x <= 11.5.0, 11.4.x <= 11.4.2, 11.3.x <= 11.3.2 fail to enforce atomic single-use consumption of guest magic link tokens, which allows an attacker with access to a valid magic link to establish multiple independent authenticated sessions via concurrent requests.. Mattermost Advisory ID: MMSA-2026-00624

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-mh4x-rmrx-3hp4 Mattermost has session spoofing due to lack of single-use consumption of guest magic link tokens enforcement
Fixes

Solution

Update Mattermost to versions 11.6.0, 10.11.13, 11.5.1, 11.4.3, 11.3.3 or higher.


Workaround

No workaround given by the vendor.

References
History

Wed, 22 Apr 2026 19:45:00 +0000

Type Values Removed Values Added
First Time appeared Mattermost mattermost Server
CPEs cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
Vendors & Products Mattermost mattermost Server

Wed, 15 Apr 2026 14:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 15 Apr 2026 13:45:00 +0000

Type Values Removed Values Added
First Time appeared Mattermost
Mattermost mattermost
Vendors & Products Mattermost
Mattermost mattermost

Wed, 15 Apr 2026 11:30:00 +0000

Type Values Removed Values Added
Description Mattermost versions 10.11.x <= 10.11.12, 11.5.x <= 11.5.0, 11.4.x <= 11.4.2, 11.3.x <= 11.3.2 fail to enforce atomic single-use consumption of guest magic link tokens, which allows an attacker with access to a valid magic link to establish multiple independent authenticated sessions via concurrent requests.. Mattermost Advisory ID: MMSA-2026-00624
Title Race Condition in Guest Magic Link Authentication Allows Token Reuse
Weaknesses CWE-367
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: Mattermost

Published:

Updated: 2026-04-15T14:00:27.030Z

Reserved: 2026-03-05T11:34:57.712Z

Link: CVE-2026-3590

cve-icon Vulnrichment

Updated: 2026-04-15T14:00:23.071Z

cve-icon NVD

Status : Analyzed

Published: 2026-04-15T12:16:40.023

Modified: 2026-04-22T19:41:52.700

Link: CVE-2026-3590

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-04-15T13:38:28Z

Weaknesses