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Mattermost EUVDEUVD-2026-77364

| CVE-2026-14344 MEDIUM
Missing Authorization (CWE-862)
2026-09-14 Mattermost GHSA-mcg5-jcfq-qfh6
Authentication Bypass Mattermost
4.3
CVSS 3.1 · Vendor: Mattermost
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Severity by source

Vendor (Mattermost) PRIMARY
4.3 MEDIUM
AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
vuln.today AI
4.3 MEDIUM

Network-reachable missing authorization requiring authenticated access (PR:L); only unauthorized board creation results, so integrity is low and neither confidentiality nor availability is impacted.

3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (Mattermost).

CVSS VectorVendor: Mattermost

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

Lifecycle Timeline

1
Analysis Generated
Sep 14, 2026 - 11:25 vuln.today

DescriptionCVE.org

Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 fail to enforce the board-creation permission which allows an unauthorized authenticated user to create boards via the board duplicate, boards-and-blocks, and archive-import endpoints.. Mattermost Advisory ID: MMSA-2026-00715

AnalysisAI

Board-creation permission enforcement is absent from three Mattermost Boards API endpoints-board duplicate, boards-and-blocks, and archive-import-allowing any authenticated user who has been denied board-creation rights to circumvent that restriction and create boards in the workspace. Affected are Mattermost versions 11.9.0, 11.8.x through 11.8.4, 11.7.x through 11.7.7, and 10.11.x through 10.11.22, as confirmed by advisory MMSA-2026-00715. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

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Exploit
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Execution
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Vulnerability AssessmentAI

Exploitation The attacker must hold valid Mattermost credentials (PR:L, authenticated user); unauthenticated access is insufficient. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The vendor-supplied CVSS 3.1 vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N and score of 4.3 correctly characterize this as a medium-severity issue: network-reachable, low attack complexity, requiring authenticated access (PR:L), and producing only a limited integrity impact with no confidentiality or availability consequence. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation Upgrade Mattermost to a version beyond the affected ranges as specified in advisory MMSA-2026-00715 at https://mattermost.com/security-updates. … Detailed patch versions, workarounds, and compensating controls in full report.
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EUVD-2026-77364 vulnerability details – vuln.today
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