Low 3.5Published Aug 17, 2026

CVE-2026-9693Mattermost thread memberships persist after team removal, exposing private channel thread metadata on re-invite

Updated under an hour ago (Oct 28, 2026, 9:40 AM ET)

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No exploitation reported and no EPSS estimate yet.

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Every CVE for Mattermost

Exploited in the last 30 days

Mattermost versions 10.11.x <= 10.11.20, 11.7.x <= 11.7.5 Mattermost fails to remove thread membership records when a user is removed from or leaves a team, which allows a previously removed user who is later re-invited to the team to view private channel thread root post content and metadata via the team threads API.. Mattermost Advisory ID: MMSA-2026-00682

CVSS: 3.5 LOW (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:N
Weakness (CWE): CWE-459
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: Aug 18, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Mattermost Mattermost mattermost:mattermost (from the name)	from 10.11.0 through 10.11.20; from 11.7.0 through 11.7.5; 11.9.0 not affected; 10.11.21 not affected; 11.7.6 not affected	CNA record
mattermost mattermost_server mattermost:mattermost_server	from 10.11.0 before 10.11.21; from 11.7.0 before 11.7.6	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.