CVE-2026-26304: Github.com/mattermost/mattermost plugin playbooks Mattermost Fails To Verify Run_create Vulnerability

MODERATE
Advisory Identifier: GHSA-4pmx-622h-x359
Share
CVSS 4.3
CWE-863
Published
Advisory Summary

CVE-2026-26304 is a MODERATE (CVSS 4.3) mattermost fails to verify run_create vulnerability (CWE-863: Incorrect Authorization) affecting Github.com/mattermost/mattermost plugin playbooks libraries in the Go ecosystem. The issue involves mattermost fails to verify run_create permission for empty playbookid. Remediation is available by upgrading affected packages to version 1.41.1-0.20260316224925-705f54a81841.

CVE-2026-26304 at a Glance

CVE Identifier CVE-2026-26304
GHSA Identifier GHSA-4pmx-622h-x359
Severity MODERATE
CVSS v3.1 Base Score 4.3
CWE Classification CWE-863: Incorrect Authorization
Affected Product Github.com/mattermost/mattermost plugin playbooks
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 4.3

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:N/I:L/A:N).

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 None (C:N)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-26304

To remediate this vulnerability, upgrade all affected Github.com/mattermost/mattermost plugin playbooks 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-plugin-playbooks fixed: 1.41.1-0.20260316224925-705f54a81841 
Upgrade github.com/mattermost/mattermost-plugin-playbooks to 1.41.1-0.20260316224925-705f54a81841
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-plugin-playbooks

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-26304, inspect your project dependencies for Github.com/mattermost/mattermost plugin playbooks:

inspect dependencies for github.com/mattermost/mattermost-plugin-playbooks

Analyze the terminal output to locate any version of Github.com/mattermost/mattermost plugin playbooks in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.41.1-0.20260316224925-705f54a81841), 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 plugin playbooks, 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 11.3.x <= 11.3.0, 11.2.x <= 11.2.2 fail to verify run_create permission for empty playbookId, which allows team members to create unauthorized runs via the playbook run API. Mattermost Advisory ID: MMSA-2025-00542

CVE-2026-26304 Affected Github.com/mattermost/mattermost plugin playbooks Versions

1 component(s)
Fixed Versions:
1.41.1-0.20260316224925-705f54a81841
Product / Package Ecosystem Affected Versions Fixed Version
github.com/mattermost/mattermost-plugin-playbooks
golang/github.com/mattermost/mattermost-plugin-playbooks
Go
< 1.41.1-0.20260316224925-705f54a81841
1.41.1-0.20260316224925-705f54a81841

References

NVD — CVE-2026-26304 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-26304
Security Fix Commit FIX COMMIT
https://github.com/mattermost/mattermost-plugin-playbooks/commit/705f54a818410f3612df3865bfde608ed471037e
Github.com/mattermost/mattermost plugin playbooks Source Repository REPOSITORY
https://github.com/mattermost/mattermost-plugin-playbooks
Github.com/mattermost/mattermost plugin playbooks Security Information SECURITY
https://mattermost.com/security-updates

Frequently Asked Questions

What is CVE-2026-26304?
CVE-2026-26304 is a security vulnerability in Github.com/mattermost/mattermost plugin playbooks involving Mattermost fails to verify run_create permission for empty playbookId under CWE-863: Incorrect Authorization.
Which Github.com/mattermost/mattermost plugin playbooks versions are affected?
Affected versions include releases prior to 1.41.1-0.20260316224925-705f54a81841 across affected packages: github.com/mattermost/mattermost-plugin-playbooks.
What version fixes CVE-2026-26304?
Upgrading to 1.41.1-0.20260316224925-705f54a81841 (or the latest patched release for your respective branch) resolves the vulnerability.
Is github.com/mattermost/mattermost-plugin-playbooks affected?
Yes, github.com/mattermost/mattermost-plugin-playbooks is affected in releases prior to 1.41.1-0.20260316224925-705f54a81841. Upgrade your dependency to 1.41.1-0.20260316224925-705f54a81841 or later.
What is the CVSS score of CVE-2026-26304?
CVE-2026-26304 has a CVSS v3.1 base score of 4.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N.
What CWE is associated with CVE-2026-26304?
CVE-2026-26304 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-2026-26304?
Run the dependency tree command: 'inspect dependencies for github.com/mattermost/mattermost-plugin-playbooks'. 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-4pmx-622h-x359",
  "modified" : "2026-03-20T22:26:12Z",
  "published" : "2026-03-16T21:34:32Z",
  "aliases" : [ "CVE-2026-26304" ],
  "summary" : "Mattermost fails to verify run_create permission for empty playbookId",
  "details" : "Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2 fail to verify run_create permission for empty playbookId, which allows team members to create unauthorized runs via the playbook run API. Mattermost Advisory ID: MMSA-2025-00542",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/mattermost/mattermost-plugin-playbooks"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.41.1-0.20260316224925-705f54a81841"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-26304"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mattermost/mattermost-plugin-playbooks/commit/705f54a818410f3612df3865bfde608ed471037e"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/mattermost/mattermost-plugin-playbooks"
  }, {
    "type" : "WEB",
    "url" : "https://mattermost.com/security-updates"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-863" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-20T22:26:12Z",
    "nvd_published_at" : "2026-03-16T20:16:17Z"
  }
}