CVE-2026-3108: Github.com/mattermost/mattermost/server/v8 Mattermost Allows Attackers To Manipulate Vulnerability
HIGHCVE-2026-3108 is a HIGH (CVSS 8.0) mattermost allows attackers to manipulate vulnerability (CWE-150: Improper Neutralization of Escape, Meta, or Control Sequences) affecting Github.com/mattermost/mattermost/server/v8 libraries in the Go ecosystem. The issue involves mattermost allows attackers to manipulate administrator terminals via crafted messages containing ansi and osc escape sequences. 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-2026-3108 at a Glance
Security Impact
CVSS: 8.0
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:R/S:C/C:H/I:H/A:H).
How to Fix CVE-2026-3108
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-2026-3108, 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-150: Improper Neutralization of Escape, Meta, or Control Sequences, where the product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could be interpreted as escape, meta, or control character sequences when they are sent to a downstream component. 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-2026-3108 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-2026-3108?
Which Github.com/mattermost/mattermost/server/v8 versions are affected?
What version fixes CVE-2026-3108?
Is github.com/mattermost/mattermost/server/v8 affected?
What is the CVSS score of CVE-2026-3108?
What CWE is associated with CVE-2026-3108?
How can I check Go dependencies for CVE-2026-3108?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-3439-vqgj-2gcf",
"modified" : "2026-03-31T23:02:57Z",
"published" : "2026-03-26T18:31:42Z",
"aliases" : [ "CVE-2026-3108" ],
"summary" : "Mattermost allows attackers to manipulate administrator terminals via crafted messages containing ANSI and OSC escape sequences",
"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 sanitize user-controlled post content in the mmctl commands terminal output which allows attackers to manipulate administrator terminals via crafted messages containing ANSI and OSC escape sequences that enable screen manipulation, fake prompts, and clipboard hijacking. Mattermost Advisory ID: MMSA-2026-00599.",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:H"
} ],
"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"
} ]
} ]
}, {
"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-2026-3108"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/mattermost/mattermost"
}, {
"type" : "WEB",
"url" : "https://mattermost.com/security-updates"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-150" ],
"severity" : "HIGH",
"github_reviewed" : true,
"github_reviewed_at" : "2026-03-31T23:02:43Z",
"nvd_published_at" : "2026-03-26T17:16:41Z"
}
}