CVE-2026-4286: Github.com/mattermost/mattermost/server/v8 Mattermost Doesn't Check If {{team_id}} Vulnerability
LOWCVE-2026-4286 is a LOW (CVSS 3.1) mattermost doesn't check if {{team_id}} vulnerability (CWE-863: Incorrect Authorization) affecting Github.com/mattermost/mattermost/server/v8 libraries in the Go ecosystem. The issue involves mattermost doesn't check if {{team_id}} was being changed when updating playbooks. Remediation is available by upgrading affected packages to version 11.5.2, 10.11.14, 1.41.1-0.20260213020129-e1d6ec2c94e6.
CVE-2026-4286 at a Glance
Security Impact
CVSS: 3.1
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N).
How to Fix CVE-2026-4286
To remediate this vulnerability, upgrade all affected Github.com/mattermost/mattermost/server/v8 dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
Upgrade github.com/mattermost/mattermost/server/v8 to 11.5.2Upgrade github.com/mattermost/mattermost/server/v8 to 10.11.14Upgrade github.com/mattermost/mattermost-plugin-playbooks to 1.41.1-0.20260213020129-e1d6ec2c94e6Run 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/v8How to Check if You Are Affected
To determine whether your application is affected by CVE-2026-4286, inspect your project dependencies for Github.com/mattermost/mattermost/server/v8:
inspect dependencies for github.com/mattermost/mattermost/server/v8Analyze the terminal output to locate any version of Github.com/mattermost/mattermost/server/v8 in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 11.5.2), 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/v8, 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
CVE-2026-4286 Affected Github.com/mattermost/mattermost/server/v8 Versions
3 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
github.com/mattermost/mattermost/server/v8
|
Go |
≥ 11.5.0
< 11.5.2
|
11.5.2
|
|
github.com/mattermost/mattermost/server/v8
|
Go |
≥ 10.11.0
< 10.11.14
|
10.11.14
|
|
github.com/mattermost/mattermost-plugin-playbooks
|
Go |
< 1.41.1-0.20260213020129-e1d6ec2c94e6
|
1.41.1-0.20260213020129-e1d6ec2c94e6
|
References
Frequently Asked Questions
What is CVE-2026-4286?
Which Github.com/mattermost/mattermost/server/v8 versions are affected?
What version fixes CVE-2026-4286?
Is github.com/mattermost/mattermost/server/v8 affected?
Is github.com/mattermost/mattermost-plugin-playbooks affected?
What is the CVSS score of CVE-2026-4286?
What CWE is associated with CVE-2026-4286?
How can I check Go dependencies for CVE-2026-4286?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-gvg4-jhmr-6j23",
"modified" : "2026-06-01T15:19:14Z",
"published" : "2026-05-18T09:31:48Z",
"aliases" : [ "CVE-2026-4286" ],
"summary" : "Mattermost doesn't check if {{team_id}} was being changed when updating playbooks",
"details" : "Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to check if {{team_id}} was being changed when updating playbooks, allowing users with only {{Manage Playbook Configurations}} permission to change a playbook's team, bypassing manage members restriction via PUT api. Mattermost Advisory ID: MMSA-2025-00552",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost/server/v8"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "11.5.0"
}, {
"fixed" : "11.5.2"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost/server/v8"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "10.11.0"
}, {
"fixed" : "10.11.14"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost-plugin-playbooks"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "1.41.1-0.20260213020129-e1d6ec2c94e6"
} ]
} ]
} ],
"references" : [ {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-4286"
}, {
"type" : "WEB",
"url" : "https://github.com/mattermost/mattermost-plugin-playbooks/commit/e1d6ec2c94e695fb74e0c0c11c0d45e028bb96f3"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/mattermost/mattermost"
}, {
"type" : "WEB",
"url" : "https://mattermost.com/security-updates"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-863" ],
"severity" : "LOW",
"github_reviewed" : true,
"github_reviewed_at" : "2026-06-01T15:19:14Z",
"nvd_published_at" : "2026-05-18T09:16:22Z"
}
}