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Mattermost EUVDEUVD-2026-60211

| CVE-2026-16044 MEDIUM
Incorrect Authorization (CWE-863)
2026-08-17 responsibledisclosure@mattermost.com GHSA-496c-r634-6cgj
Mattermost Authentication Bypass Mattermost Server
5.4
CVSS 3.1 · Vendor: mattermost
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Severity by source

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

Board Admin escalation implies read access to all board content, warranting C:L; availability is unaffected by the privilege grant itself.

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

Primary rating from Vendor (mattermost).

CVSS VectorVendor: mattermost

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
Low

Lifecycle Timeline

1
Analysis Generated
Aug 17, 2026 - 15:34 vuln.today

DescriptionCVE.org

Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21 fail to prevent guest users from receiving Board Admin privileges during board archive import which allows a board member to escalate a guest user to Board Admin via importing a crafted .boardarchive file. Mattermost Advisory ID: MMSA-2026-00672

AnalysisAI

Privilege escalation in Mattermost's Boards feature allows a low-privileged board member to elevate a guest user to Board Admin by importing a specially crafted .boardarchive file. Affected are Mattermost versions 10.11.0 through 10.11.21 and 11.7.0 through 11.7.6. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

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Delivery
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Exploit
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Execution
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Vulnerability AssessmentAI

Exploitation The attacker must hold at minimum a board member role on the target Mattermost instance - unauthenticated exploitation is not possible per the PR:L CVSS metric. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 5.4 Medium score is broadly consistent with actual risk: network-reachable, low complexity, but gated behind existing board membership (PR:L). … 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 for each branch: beyond 11.7.6 for the 11.7.x branch and beyond 10.11.21 for the 10.11.x branch, per the vendor's security updates page at https://mattermost.com/security-updates. … Detailed patch versions, workarounds, and compensating controls in full report.
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EUVD-2026-60211 vulnerability details – vuln.today
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