CVE-2026-7387: Github.com/mattermost/mattermost server Mattermost Doesn't Require Role-management Authorization Vulnerability

HIGH
Advisory Identifier: GHSA-6hxm-w4hv-vgvw
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CVSS 8.8
CWE-863
Published
Advisory Summary

CVE-2026-7387 is a HIGH (CVSS 8.8) mattermost doesn't require role-management authorization vulnerability (CWE-863: Incorrect Authorization) affecting Github.com/mattermost/mattermost server libraries in the Go ecosystem. The issue involves mattermost doesn't require role-management authorization when setting the scheme_admin flag on group syncable link and patch endpoints. Remediation is available by upgrading affected packages to version 11.6.1, 8.0.0-20260506065351-202d125afa87, 11.5.5, 10.11.17.

CVE-2026-7387 at a Glance

CVE Identifier CVE-2026-7387
GHSA Identifier GHSA-6hxm-w4hv-vgvw
Severity HIGH
CVSS v3.1 Base Score 8.8
CWE Classification CWE-863: Incorrect Authorization
Affected Product Github.com/mattermost/mattermost server
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 8.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2026-7387

To remediate this vulnerability, upgrade all affected Github.com/mattermost/mattermost server dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

github.com/mattermost/mattermost-server fixed: 11.6.1 
Upgrade github.com/mattermost/mattermost-server to 11.6.1
github.com/mattermost/mattermost/server/v8 fixed: 8.0.0-20260506065351-202d125afa87 
Upgrade github.com/mattermost/mattermost/server/v8 to 8.0.0-20260506065351-202d125afa87
github.com/mattermost/mattermost-server fixed: 11.5.5 
Upgrade github.com/mattermost/mattermost-server to 11.5.5
github.com/mattermost/mattermost-server fixed: 10.11.17 
Upgrade github.com/mattermost/mattermost-server to 10.11.17
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for github.com/mattermost/mattermost-server

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-7387, inspect your project dependencies for Github.com/mattermost/mattermost server:

inspect dependencies for github.com/mattermost/mattermost-server

Analyze the terminal output to locate any version of Github.com/mattermost/mattermost server in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 11.6.1), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-863: Incorrect Authorization, where the product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. In Github.com/mattermost/mattermost server, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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 scheme_admin 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

CVE-2026-7387 Affected Github.com/mattermost/mattermost server Versions

4 component(s)
Fixed Versions:
11.6.18.0.0-20260506065351-202d125afa8711.5.510.11.17
Product / Package Ecosystem Affected Versions Fixed Version
github.com/mattermost/mattermost-server
golang/github.com/mattermost/mattermost-server
Go
≥ 11.6.0
< 11.6.1
All 1 versions
11.6.0
11.6.1
github.com/mattermost/mattermost/server/v8
golang/github.com/mattermost/mattermost/server/v8
Go
≥ 8.0.0-20250731163400-5b955468ea1e
< 8.0.0-20260506065351-202d125afa87
8.0.0-20260506065351-202d125afa87
github.com/mattermost/mattermost-server
golang/github.com/mattermost/mattermost-server
Go
≥ 11.5.0
< 11.5.5
11.5.5
github.com/mattermost/mattermost-server
golang/github.com/mattermost/mattermost-server
Go
≥ 10.11.0
< 10.11.17
10.11.17

References

NVD — CVE-2026-7387 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-7387
Github.com/mattermost/mattermost server Source Repository REPOSITORY
https://github.com/mattermost/mattermost/pull/36434
Github.com/mattermost/mattermost server Source Repository REPOSITORY
https://github.com/mattermost/mattermost/pull/36432
Github.com/mattermost/mattermost server Source Repository REPOSITORY
https://github.com/mattermost/mattermost/pull/36431
Github.com/mattermost/mattermost server Source Repository REPOSITORY
https://github.com/mattermost/mattermost/pull/36423
Github.com/mattermost/mattermost server Source Repository REPOSITORY
https://github.com/mattermost/mattermost/pull/36316
Security Fix Commit FIX COMMIT
https://github.com/mattermost/mattermost/commit/d5f29c8ebbeb04460d16d9e2635ce50deeb78428
Security Fix Commit FIX COMMIT
https://github.com/mattermost/mattermost/commit/a9e574a82633915f22071f0d7ca2b006f249ec2a
Security Fix Commit FIX COMMIT
https://github.com/mattermost/mattermost/commit/8c72083414e675c97987374395e36d1f36b4bd8a
Security Fix Commit FIX COMMIT
https://github.com/mattermost/mattermost/commit/202d125afa87fe39611686850fd82590c99ca344
Security Fix Commit FIX COMMIT
https://github.com/mattermost/mattermost/commit/1ce2484a00c9821ee19708d2c46720e4855033a9
Github.com/mattermost/mattermost server Release RELEASE
https://github.com/mattermost/mattermost/releases/tag/v10.11.16
Github.com/mattermost/mattermost server Release RELEASE
https://github.com/mattermost/mattermost/releases/tag/v11.5.5
Github.com/mattermost/mattermost server Release RELEASE
https://github.com/mattermost/mattermost/releases/tag/v11.6.2
Github.com/mattermost/mattermost server Release RELEASE
https://github.com/mattermost/mattermost/releases/tag/v11.7.0
Github.com/mattermost/mattermost server Security Information SECURITY
https://mattermost.com/security-updates
Github.com/mattermost/mattermost server Source Repository REPOSITORY
https://github.com/mattermost/mattermost

Frequently Asked Questions

What is CVE-2026-7387?
CVE-2026-7387 is a security vulnerability in Github.com/mattermost/mattermost server involving Mattermost doesn't require role-management authorization when setting the scheme_admin flag on group syncable link and patch endpoints under CWE-863: Incorrect Authorization.
Which Github.com/mattermost/mattermost server versions are affected?
Affected versions include releases prior to 11.6.1, 8.0.0-20260506065351-202d125afa87, 11.5.5, 10.11.17 across affected packages: github.com/mattermost/mattermost-server, github.com/mattermost/mattermost/server/v8.
What version fixes CVE-2026-7387?
Upgrading to 11.6.1, 8.0.0-20260506065351-202d125afa87, 11.5.5, 10.11.17 (or the latest patched release for your respective branch) resolves the vulnerability.
Is github.com/mattermost/mattermost-server affected?
Yes, github.com/mattermost/mattermost-server is affected in releases prior to 11.6.1, 11.5.5, 10.11.17. Upgrade your dependency to 11.6.1, 11.5.5, 10.11.17 or later.
Is github.com/mattermost/mattermost/server/v8 affected?
Yes, github.com/mattermost/mattermost/server/v8 is affected in releases prior to 8.0.0-20260506065351-202d125afa87. Upgrade your dependency to 8.0.0-20260506065351-202d125afa87 or later.
What is the CVSS score of CVE-2026-7387?
CVE-2026-7387 has a CVSS v3.1 base score of 8.8 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2026-7387?
CVE-2026-7387 is classified under CWE-863: Incorrect Authorization (The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.).
How can I check Go dependencies for CVE-2026-7387?
Run the dependency tree command: 'inspect dependencies for github.com/mattermost/mattermost-server'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-6hxm-w4hv-vgvw",
  "modified" : "2026-08-24T21:51:47Z",
  "published" : "2026-06-12T18:31:59Z",
  "aliases" : [ "CVE-2026-7387" ],
  "summary" : "Mattermost doesn't require role-management authorization when setting the scheme_admin flag on group syncable link and patch endpoints",
  "details" : "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 scheme_admin 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",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/mattermost/mattermost-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "11.6.0"
      }, {
        "fixed" : "11.6.1"
      } ]
    } ],
    "versions" : [ "11.6.0" ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/mattermost/mattermost-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "11.5.0"
      }, {
        "fixed" : "11.5.5"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 11.5.4"
    }
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/mattermost/mattermost-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "10.11.0"
      }, {
        "fixed" : "10.11.17"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 10.11.15"
    }
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/mattermost/mattermost/server/v8"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "8.0.0-20250731163400-5b955468ea1e"
      }, {
        "fixed" : "8.0.0-20260506065351-202d125afa87"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-7387"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mattermost/mattermost/pull/36434"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mattermost/mattermost/pull/36432"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mattermost/mattermost/pull/36431"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mattermost/mattermost/pull/36423"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mattermost/mattermost/pull/36316"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mattermost/mattermost/commit/d5f29c8ebbeb04460d16d9e2635ce50deeb78428"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mattermost/mattermost/commit/a9e574a82633915f22071f0d7ca2b006f249ec2a"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mattermost/mattermost/commit/8c72083414e675c97987374395e36d1f36b4bd8a"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mattermost/mattermost/commit/202d125afa87fe39611686850fd82590c99ca344"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mattermost/mattermost/commit/1ce2484a00c9821ee19708d2c46720e4855033a9"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mattermost/mattermost/releases/tag/v10.11.16"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mattermost/mattermost/releases/tag/v11.5.5"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mattermost/mattermost/releases/tag/v11.6.2"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mattermost/mattermost/releases/tag/v11.7.0"
  }, {
    "type" : "WEB",
    "url" : "https://mattermost.com/security-updates"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/mattermost/mattermost"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-863" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-24T21:51:47Z",
    "nvd_published_at" : "2026-06-12T17:16:27Z"
  }
}