Medium 5.4Published Jul 13, 2026

CVE-2026-9597Deactivated guest accounts can authenticate via magic-link token in Mattermost REST API login endpoint

Updated under an hour ago (Oct 26, 2026, 9:40 PM ET)

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It affects Mattermost and 1 other product. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4 fail to verify whether a guest account is deactivated before creating a session in the magic-link token login path, which allows a deactivated guest user to obtain a fully functional session via a magic-link token issued prior to deactivation.. Mattermost Advisory ID: MMSA-2026-00681

CVSS: 5.4 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Weakness (CWE): CWE-305
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Mattermost
NVD analysis: Analyzed
Record last updated: Jul 13, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Mattermost Mattermost mattermost:mattermost (from the name)	from 11.7.0 through 11.7.2; from 11.6.0 through 11.6.4; 11.8.0 not affected; 11.7.3 not affected; 11.6.5 not affected	CNA record
mattermost mattermost_server mattermost:mattermost_server	from 11.6.0 before 11.6.5; from 11.7.0 before 11.7.3	NVD

References

References

https://mattermost.com/security-updates	vendor-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.