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High, CVSS 8.8amended

Mattermost doesn't require role-management authorization when setting the scheme_admin flag on group syncable link and patch endpoints

CVE-2026-7387GHSA-6hxm-w4hv-vgvw

What to do

Partial vendor fix. Follow the primary source's mitigation guidance and check back for a fix.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • Go github.com/mattermost/mattermost/server/v8

    Affected
    >= 8.0.0-20250731163400-5b955468ea1e, < 8.0.0-20260506065351-202d125afa87
    Fixed in
    8.0.0-20260506065351-202d125afa87

  • Go github.com/mattermost/mattermost-server/v6

    Affected
    every version
    Fixed in
    no fixed version recorded

  • Go github.com/mattermost/mattermost-server

    Affected
    >= 11.6.0, <= 11.6.0>= 11.5.0, <= 11.5.4>= 10.11.0, <= 10.11.15
    Fixed in
    10.11.17, 11.5.5, 11.6.1

  • Go github.com/mattermost/mattermost-server/v5

    Affected
    every version
    Fixed in
    no fixed version recorded

Sources

  • Open Source Vulnerabilities (OSV.dev), including the GitHub Advisory Database

    OSV record GO-2026-6280 lists affected ranges: Go github.com/mattermost/mattermost-server >=10.11.0+incompatible =11.5.0+incompatible =11.6.0+incompatible =0; Go github.com/mattermost/mattermost-server/v6 >=0; Go github.com/mattermost/mattermost/server/v8 >=8.0.0-20250731163400-5b955468ea1e <8.0.0-20260506065351-202d125afa87 (fixed)

    VerifiedObserved Structured OSV record; not marked as GitHub-reviewed.

  • GitHub Advisory Database and maintainer security advisories on GitHub

    GitHub-reviewed advisory GHSA-6hxm-w4hv-vgvw lists affected ranges: Go github.com/mattermost/mattermost-server >=11.6.0 =11.5.0 =10.11.0 =8.0.0-20250731163400-5b955468ea1e <8.0.0-20260506065351-202d125afa87

    VerifiedObserved Structured GitHub Advisory Database record (type=reviewed) from the GitHub REST API.

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
8.8 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS
  • CVE-2026-7387: 0.31% estimated exploitation activity in the next 30 days; percentile 23.90 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 fail to require role-management authorization when setting the schemeadmin flag on group syncable link and patch endpoints, which allows a user with group-link permissions to escalate themselves and group members to team or channel admin via crafted API requests. Mattermost Advisory ID: MMSA-2026-00665

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-6hxm-w4hv-vgvw

  2. Revision 1 · created ·

    Published from osv record GO-2026-6280

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-7387

Advisory: Mattermost doesn't require role-management authorization when setting the scheme_admin flag on group syncable link and patch endpoints
IDs: CVE-2026-7387, GHSA-6hxm-w4hv-vgvw
Record: https://patchnext.com/advisories/cve-2026-7387 (revision 2, source checked 26 Oct 2026, 15:28 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: github.com/mattermost/mattermost/server/v8 8.0.0-20260506065351-202d125afa87; github.com/mattermost/mattermost-server 11.6.1, 11.5.5, 10.11.17. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/mattermost/mattermost/server/v8: affected >= 8.0.0-20250731163400-5b955468ea1e, < 8.0.0-20260506065351-202d125afa87; fixed in 8.0.0-20260506065351-202d125afa87
- Go github.com/mattermost/mattermost-server/v6: affected every version
- Go github.com/mattermost/mattermost-server: affected >= 11.6.0, <= 11.6.0; >= 11.5.0, <= 11.5.4; >= 10.11.0, <= 10.11.15; fixed in 10.11.17, 11.5.5, 11.6.1
- Go github.com/mattermost/mattermost-server/v5: affected every version

## Suggested inspection (read-only)
- Go github.com/mattermost/mattermost/server/v8: check the installed version with your package manager.
- Go github.com/mattermost/mattermost-server/v6: check the installed version with your package manager.
- Go github.com/mattermost/mattermost-server: check the installed version with your package manager.
- Go github.com/mattermost/mattermost-server/v5: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/mattermost/mattermost/server/v8, github.com/mattermost/mattermost-server/v6, github.com/mattermost/mattermost-server, github.com/mattermost/mattermost-server/v5.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GO-2026-6280 (OSV record GO-2026-6280 lists affected ranges: Go github.com/mattermost/mattermost-server >=10.11.0+incompatible =11.5.0+incompatible =11.6.0+incompatible =0; Go github.com/mattermost/mattermost-server/v6 >=0; Go github.com/mattermost/mattermost/server/v8 >=8.0.0-20250731163400-5b955468ea1e <8.0.0-20260506065351-202d125afa87 (fixed))
- Verified: https://github.com/advisories/GHSA-6hxm-w4hv-vgvw (GitHub-reviewed advisory GHSA-6hxm-w4hv-vgvw lists affected ranges: Go github.com/mattermost/mattermost-server >=11.6.0 =11.5.0 =10.11.0 =8.0.0-20250731163400-5b955468ea1e <8.0.0-20260506065351-202d125afa87)

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