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    CVE-2026-9859

    Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to enforce PermissionManageBoardRoles on the channelId field of the batch endpoint, which allows an authenticated board editor to relink any board they can edit to an arbitrary channel via a crafted PATCH request. Mattermost Advisory ID: MMSA-2026-00686

    Published:Aug 17, 2026
    Last Modified:Aug 19, 2026
    EPS:Aug 17, 2026
    EPSS Score:0.00253
    CVSS Score:6.5

    Affected Products

    Vendor
    Mattermost
    Product
    Mattermost
    Vendor
    Mattermost
    Product
    Mattermost Server

    Exploits

    No exploit reference

    Common Weakness Enumeration

    CWE-863 Incorrect Authorization

    Common Attack Pattern Enumeration and Classification (CAPEC)

    No CAPEC recorded yet

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    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High