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CVE-2026-15754

Missing per-channel team-scope check in ABAC access control policy unassign allows cross-team policy removal

Published: Aug 17, 2026Updated: Aug 18, 2026 Sources: CVE List NVDCWE-863
4.2MEDIUM
NVD MITRE
EPSS Score
0.1%
Top 95.6%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
OpenVAS

Description

Mattermost versions 11.7.x <= 11.7.6, 11.8.x <= 11.8.3 The access control policy unassign endpoint fails to re-validate that each target channel still belongs to the requesting admin's team, which allows an authenticated team administrator to remove ABAC (attribute-based access control) policy assignments from channels outside their team via the policy unassign API after a channel has been moved to another team.. Mattermost Advisory ID: MMSA-2026-00718

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:HPR:HUI:RS:UC:NI:HA:N
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:HPrivileges Required
High
UI:RUser Interaction
Required
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:HIntegrity
High
A:NAvailability
None
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Weaknesses

CWE-863

Affected Products

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

Exploitability

Official Patch Available
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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

2 techniques
Initial Access
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References

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

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