CVE-2026-6347: Github.com/mattermost/mattermost server Mattermost Doesn't Sanitize Sensitive Configuration Vulnerability
HIGHCVE-2026-6347 is a HIGH (CVSS 7.6) mattermost doesn't sanitize sensitive configuration vulnerability (CWE-200: Exposure of Sensitive Information to an Unauthorized Actor) affecting Github.com/mattermost/mattermost server libraries in the Go ecosystem. The issue involves mattermost doesn't sanitize sensitive configuration fields in the mattermost calls plugin. Remediation is available by upgrading affected packages to version 11.5.2, 10.11.14, 11.4.4, 1.12.0-rc2.
CVE-2026-6347 at a Glance
Security Impact
CVSS: 7.6
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:L).
How to Fix CVE-2026-6347
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.
Upgrade github.com/mattermost/mattermost-server to 11.5.2Upgrade github.com/mattermost/mattermost-server to 10.11.14Upgrade github.com/mattermost/mattermost-server to 11.4.4Upgrade github.com/mattermost/mattermost-plugin-calls to 1.12.0-rc2Run the following command in your project directory to verify that all resolved dependencies use the patched release:
inspect dependencies for github.com/mattermost/mattermost-serverHow to Check if You Are Affected
To determine whether your application is affected by CVE-2026-6347, inspect your project dependencies for Github.com/mattermost/mattermost server:
inspect dependencies for github.com/mattermost/mattermost-serverAnalyze 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 11.5.2), 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-200: Exposure of Sensitive Information to an Unauthorized Actor, where the product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. 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
CVE-2026-6347 Affected Github.com/mattermost/mattermost server Versions
4 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
github.com/mattermost/mattermost-server
|
Go |
≥ 11.5.0
< 11.5.2
|
11.5.2
|
|
github.com/mattermost/mattermost-server
|
Go |
≥ 10.11.0
< 10.11.14
|
10.11.14
|
|
github.com/mattermost/mattermost-server
|
Go |
≥ 11.4.0
< 11.4.4
|
11.4.4
|
|
github.com/mattermost/mattermost-plugin-calls
|
Go |
< 1.12.0-rc2
|
1.12.0-rc2
|
References
Frequently Asked Questions
What is CVE-2026-6347?
Which Github.com/mattermost/mattermost server versions are affected?
What version fixes CVE-2026-6347?
Is github.com/mattermost/mattermost-server affected?
Is github.com/mattermost/mattermost-plugin-calls affected?
What is the CVSS score of CVE-2026-6347?
What CWE is associated with CVE-2026-6347?
How can I check Go dependencies for CVE-2026-6347?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-82j6-4fq7-fx62",
"modified" : "2026-06-01T15:44:49Z",
"published" : "2026-05-18T09:31:48Z",
"aliases" : [ "CVE-2026-6347" ],
"summary" : "Mattermost doesn't sanitize sensitive configuration fields in the Mattermost Calls plugin ",
"details" : "Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to sanitize sensitive configuration fields in the Mattermost Calls plugin which allows an attacker with access to a support packet to obtain TURN server credentials via the plaintext values present in the exported plugin configuration.. Mattermost Advisory ID: MMSA-2026-00605",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:L"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost-server"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "11.5.0"
}, {
"fixed" : "11.5.2"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost-server"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "10.11.0"
}, {
"fixed" : "10.11.14"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost-server"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "11.4.0"
}, {
"fixed" : "11.4.4"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost-plugin-calls"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "1.12.0-rc2"
} ]
} ]
} ],
"references" : [ {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-6347"
}, {
"type" : "WEB",
"url" : "https://github.com/mattermost/mattermost-plugin-calls/commit/d48893c8558e5a61f5fdd188bbee5ec7cb73887b"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/mattermost/mattermost"
}, {
"type" : "WEB",
"url" : "https://mattermost.com/security-updates"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-200" ],
"severity" : "HIGH",
"github_reviewed" : true,
"github_reviewed_at" : "2026-06-01T15:44:48Z",
"nvd_published_at" : "2026-05-18T09:16:24Z"
}
}