CVE-2026-3590
Mattermost has session spoofing due to lack of single-use consumption of guest magic link tokens enforcement
6.5
MEDIUM
CVSS 3.1
EPSS 0.04%
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.
How to fix CVE-2026-3590
To remediate CVE-2026-3590, upgrade the affected package to a fixed version below.
- —upgrade to 10.11.13 or later
- —upgrade to 8.0.0-20250723052842-4cb8d8940332 or later
Is CVE-2026-3590 being exploited?
Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.
Affected packages (2)
- >= 10.11.0-rc1, < 10.11.13
- >= 8.0.0-20250721062209-4952acea88ce, < 8.0.0-20250723052842-4cb8d8940332
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N |