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    CVE-2026-95666

    Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to limit the length of the post ID array accepted by the bulk reactions endpoint which allows an authenticated user to cause excessive database load via a crafted request to {{POST /api/v4/posts/ids/reactions}}.. Mattermost Advisory ID: MMSA-2026-00771

    Published:Sep 22, 2026
    Last Modified:Oct 7, 2026
    EPS:Sep 22, 2026
    EPSS Score:0.00359
    CVSS Score:4.3

    Affected Products

    Vendor
    Mattermost
    Product
    Mattermost
    Vendor
    Mattermost
    Product
    Mattermost Server

    Exploits

    No exploit reference

    Related CVEs

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    CVE-2026-93848 (CVSS 2.7) — Mattermost versions 11.7.x <= 11.7.10 fail to apply outbound internal-connection filtering to the OpenID disco…
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    CVE-2026-93847 (CVSS 3.5) — Mattermost versions 11.7.x <= 11.7.10 fail to validate reserved system post types on the scheduled post creati…
    CVE-2026-116516 (CVSS 6.5) — Mattermost versions <=11.9 11.1.9 11.5.8 11.10.7.0 fail to validate Zoom chat line length before slicing which…
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    CVE-2026-18799 (CVSS 4.3) — Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to restrict …
    CVE-2026-16251 (CVSS 6.5) — Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to limit the…

    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