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    CVE-2026-5139

    Mattermost versions 11.7.x <= 11.7.0, 11.6.x <= 11.6.2, 11.5.x <= 11.5.5, 10.11.x <= 10.11.17 fail to enforce administrator authorization on the {{setDefaultInstance}} call within the {{/gitlab connect}} command handler, which allows any authenticated user to overwrite the global default GitLab instance configuration via the {{/gitlab connect <instance-name>}} slash command.. Mattermost Advisory ID: MMSA-2026-00644

    Published:Jun 22, 2026
    Last Modified:Jun 22, 2026
    EPS:Jun 22, 2026
    EPSS Score:
    CVSS Score:5.4

    Affected Products

    Vendor
    Mattermost
    Product
    Mattermost

    Exploits

    No exploit reference

    Common Weakness Enumeration

    CWE-862 Missing Authorization

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-665 Exploitation of Thunderbolt Protection Flaws

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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