CVE-2026-3590

Race Condition in Guest Magic Link Authentication Allows Token Reuse

Published Apr 15, 2026 CVSS 3.1 · 6.5 Medium EPSS < 1% KEV · Not listed
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

Remediation

Vendor Solution

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

Tracking

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

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

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

Weaknesses

Sources

Status
PUBLISHED
Assigner
Mattermost
Published
Updated
Apr 15, 2026, 2:00 PM
Reserved
Mar 5, 2026, 11:34 AM
Status
Analyzed
Published
Apr 15, 2026, 12:16 PM
Modified
Nov 11, 2026, 11:10 PM