CVE Feed

    Dashboard / CVE / CVE-2026-18551

    CVE-2026-18551

    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 validate the combination of guest and admin scheme roles which allows an authenticated attacker to escalate a guest account to team or channel admin via a crafted PUT request to the member roles API endpoint.. Mattermost Advisory ID: MMSA-2026-00752

    Published:Oct 16, 2026
    Last Modified:Oct 29, 2026
    EPS:Oct 16, 2026
    EPSS Score:0.00222
    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

    Related CVEs

    CVE-2026-93851 (CVSS 8) — Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10 fail to validate the target post ID …
    CVE-2026-93846 (CVSS 3.8) — Mattermost versions 11.7.x <= 11.7.10 fail to restrict which built-in roles can be assigned to a team member v…
    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…
    CVE-2026-93850 (CVSS 6.5) — 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 bind the…
    CVE-2026-93849 (CVSS 6.5) — 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 Mattermost fail …
    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…
    CVE-2026-13411 (CVSS 4.3) — Mattermost versions 11.7.x <= 11.7.11 fail to validate null elements when decoding playbook import conditions …
    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