CVE-2026-6346: Github.com/mattermost/mattermost/server/v8 Mattermost Doesn't Sanitize Sensitive Configuration Vulnerability
HIGHCVE-2026-6346 is a HIGH (CVSS 8.7) mattermost doesn't sanitize sensitive configuration vulnerability (CWE-200: Exposure of Sensitive Information to an Unauthorized Actor) affecting Github.com/mattermost/mattermost/server/v8 libraries in the Go ecosystem. The issue involves mattermost doesn't sanitize sensitive configuration fields before including them in support packet generation. Remediation is available by upgrading affected packages to version 11.5.2, 10.11.14, 11.4.4, 8.0.0-20260326202606-fac92f4a71f3, 5.3.2-0.20260326202606-fac92f4a71f3.
CVE-2026-6346 at a Glance
Security Impact
CVSS: 8.7
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:H/A:N).
How to Fix CVE-2026-6346
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/server/v8 to 11.4.4Upgrade github.com/mattermost/mattermost/server/v8 to 8.0.0-20260326202606-fac92f4a71f3Upgrade github.com/mattermost/mattermost-server to 5.3.2-0.20260326202606-fac92f4a71f3Run 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-2026-6346, 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-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/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-2026-6346 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 |
≥ 11.5.0
< 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/server/v8
|
Go |
≥ 11.4.0
< 11.4.4
|
11.4.4
|
|
github.com/mattermost/mattermost/server/v8
|
Go |
< 8.0.0-20260326202606-fac92f4a71f3
|
8.0.0-20260326202606-fac92f4a71f3
|
|
github.com/mattermost/mattermost-server
|
Go |
< 5.3.2-0.20260326202606-fac92f4a71f3
|
5.3.2-0.20260326202606-fac92f4a71f3
|
References
Frequently Asked Questions
What is CVE-2026-6346?
Which Github.com/mattermost/mattermost/server/v8 versions are affected?
What version fixes CVE-2026-6346?
Is github.com/mattermost/mattermost/server/v8 affected?
Is github.com/mattermost/mattermost-server affected?
What is the CVSS score of CVE-2026-6346?
What CWE is associated with CVE-2026-6346?
How can I check Go dependencies for CVE-2026-6346?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-9p64-jpc7-m2rp",
"modified" : "2026-06-01T15:41:08Z",
"published" : "2026-05-18T09:31:48Z",
"aliases" : [ "CVE-2026-6346" ],
"summary" : "Mattermost doesn't sanitize sensitive configuration fields before including them in support packet generation",
"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 before including them in support packet generation, which allows a Mattermost System Admin or any party with access to a support packet to obtain sensitive credentials in plaintext via downloading a support packet from the System Console.. Mattermost Advisory ID: MMSA-2026-00607",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/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/server/v8"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "11.4.0"
}, {
"fixed" : "11.4.4"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost/server/v8"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "8.0.0-20260326202606-fac92f4a71f3"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost-server"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "5.3.2-0.20260326202606-fac92f4a71f3"
} ]
} ]
} ],
"references" : [ {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-6346"
}, {
"type" : "WEB",
"url" : "https://github.com/mattermost/mattermost/commit/fac92f4a71f356009e27983a980f729f599e8ba5"
}, {
"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" : "2026-06-01T15:41:08Z",
"nvd_published_at" : "2026-05-18T09:16:24Z"
}
}