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CVE-2026-9693

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

Published: Aug 17, 2026Updated: Aug 19, 2026 Sources: CVE List NVDCWE-459
3.5LOW
NVD MITRE
EPSS Score
0.2%
Top 94.7%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
OpenVAS

Description

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

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:LUI:RS:UC:LI:NA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:LPrivileges Required
Low
UI:RUser Interaction
Required
Scope
S:UScope
Unchanged
Impact
C:LConfidentiality
Low
I:NIntegrity
None
A:NAvailability
None
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Weaknesses

CWE-459

Affected Products

Mattermost
commercial·US
MattermostOn-premWeb App
Communications / messaging-chat
mattermost serverOn-premWeb App
Communications / messaging-chat

Exploitability

Official Patch Available
Is your org exposed to CVE-2026-9693?We can run the check for you — a free external exposure review, no install. Check my exposure

References

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

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