EUVD-2026-60212
GHSA-mg83-f953-3vq5
Severity by source
AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:H/A:N
Network-accessible API (AV:N), team-admin credentials required (PR:H), channel-move prerequisite raises complexity (AC:H), and impact is solely unauthorized policy modification (I:H, C:N, A:N).
Primary rating from Vendor (mattermost).
CVSS VectorVendor: mattermost
Lifecycle Timeline
1DescriptionCVE.org
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
AnalysisAI
Incorrect authorization in Mattermost's ABAC policy unassign API endpoint allows an authenticated team administrator to remove attribute-based access control policy assignments from channels that no longer belong to their team. Affected releases are Mattermost 11.7.0 through 11.7.6 and 11.8.0 through 11.8.3, tracked as MMSA-2026-00718 (ENISA EUVD-2026-60212). …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the attacker to hold an authenticated team administrator account within Mattermost (PR:H per CVSS vector). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 score of 4.2 (Medium) accurately reflects the constrained exploitation profile: Attack Complexity is High (AC:H) because successful abuse requires a channel to have already been moved to a different team, creating a narrow and often transient window; Privileges Required is High (PR:H) because the attacker must hold team administrator credentials; and User Interaction is Required (UI:R), adding a further dependency on organizational workflow events. … 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 server to a release that addresses MMSA-2026-00718; consult the vendor security updates page at https://mattermost.com/security-updates for the specific patched version, as an exact fix version number was not independently confirmed in the available intelligence (patch available per vendor advisory). … Detailed patch versions, workarounds, and compensating controls in full report. |
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Same weakness CWE-863 – Incorrect Authorization
View allSame technique Authentication Bypass
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External POC / Exploit Code
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