CVE-2026-4274: Github.com/mattermost/mattermost/server/v8 Mattermost Has An Incorrect Authorization Vulnerability
MODERATECVE-2026-4274 is a MODERATE (CVSS 5.4) mattermost has an incorrect authorization vulnerability (CWE-863: Incorrect Authorization) affecting Github.com/mattermost/mattermost/server/v8 libraries in the Go ecosystem. The issue involves mattermost has an incorrect authorization issue. Remediation is available by upgrading affected packages to version 11.4.1, 11.3.2, 11.2.3, 10.11.11, 8.0.0-20260217110922-b7d4a1f1f59b.
CVE-2026-4274 at a Glance
Security Impact
CVSS: 5.4
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:L/I:L/A:N).
How to Fix CVE-2026-4274
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 11.4.1Upgrade github.com/mattermost/mattermost/server/v8 to 11.3.2Upgrade github.com/mattermost/mattermost/server/v8 to 11.2.3Upgrade github.com/mattermost/mattermost/server/v8 to 10.11.11Upgrade github.com/mattermost/mattermost/server/v8 to 8.0.0-20260217110922-b7d4a1f1f59bRun 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-2026-4274, 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 11.4.1), 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/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-2026-4274 Affected Github.com/mattermost/mattermost/server/v8 Versions
5 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
github.com/mattermost/mattermost/server/v8
|
Go |
≥ 11.4.0-rc1
< 11.4.1
|
11.4.1
|
|
github.com/mattermost/mattermost/server/v8
|
Go |
≥ 11.3.0-rc1
< 11.3.2
|
11.3.2
|
|
github.com/mattermost/mattermost/server/v8
|
Go |
≥ 11.2.0-rc1
< 11.2.3
|
11.2.3
|
|
github.com/mattermost/mattermost/server/v8
|
Go |
≥ 10.11.0-rc1
< 10.11.11
|
10.11.11
|
|
github.com/mattermost/mattermost/server/v8
|
Go |
≥ 8.0.0-20260105080200-d27a2195068d
< 8.0.0-20260217110922-b7d4a1f1f59b
|
8.0.0-20260217110922-b7d4a1f1f59b
|
References
Frequently Asked Questions
What is CVE-2026-4274?
Which Github.com/mattermost/mattermost/server/v8 versions are affected?
What version fixes CVE-2026-4274?
Is github.com/mattermost/mattermost/server/v8 affected?
What is the CVSS score of CVE-2026-4274?
What CWE is associated with CVE-2026-4274?
How can I check Go dependencies for CVE-2026-4274?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-g7fp-cqj5-x8hf",
"modified" : "2026-03-31T23:01:25Z",
"published" : "2026-03-26T12:30:29Z",
"aliases" : [ "CVE-2026-4274" ],
"summary" : "Mattermost has an Incorrect Authorization issue",
"details" : "Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to restrict team-level access when processing membership sync from a remote cluster, which allows a malicious remote cluster to grant a user access to an entire private team instead of only the shared channel via sending crafted membership sync messages that trigger team membership assignment. Mattermost Advisory ID: MMSA-2026-00574",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost/server/v8"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "11.4.0-rc1"
}, {
"fixed" : "11.4.1"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost/server/v8"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "11.3.0-rc1"
}, {
"fixed" : "11.3.2"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost/server/v8"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "11.2.0-rc1"
}, {
"fixed" : "11.2.3"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost/server/v8"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "10.11.0-rc1"
}, {
"fixed" : "10.11.11"
} ]
} ],
"database_specific" : {
"last_known_affected_version_range" : "< 10.11.1"
}
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost/server/v8"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "8.0.0-20260105080200-d27a2195068d"
}, {
"fixed" : "8.0.0-20260217110922-b7d4a1f1f59b"
} ]
} ]
} ],
"references" : [ {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-4274"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/mattermost/mattermost"
}, {
"type" : "WEB",
"url" : "https://mattermost.com/security-updates"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-863" ],
"severity" : "MODERATE",
"github_reviewed" : true,
"github_reviewed_at" : "2026-03-31T23:01:25Z",
"nvd_published_at" : "2026-03-26T11:16:21Z"
}
}