CVE-2026-3590

Race Condition in Guest Magic Link Authentication Allows Token Reuse

State: Published
Severity: 6.5 Medium
Published: Apr 15, 2026
Updated: Apr 15, 2026
Reserved: Mar 5, 2026

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

Scores

CVSS	Score	Vector	Source
3.1	6.5 Medium	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N	Mattermost

Weaknesses

CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition

Affected Products

Product	Versions
MattermostMattermost	10.11.0 through 10.11.12Affected 11.5.0 through 11.5.0Affected 11.4.0 through 11.4.2Affected 11.3.0 through 11.3.2Affected 11.6.0Not affected 10.11.13Not affected 11.5.1Not affected 11.4.3Not affected 11.3.3Not affected

References

MMSA-2026-00624vendor-advisory

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