CVE-2026-3114: Github.com/mattermost/mattermost/server/v8 Mattermost Doesn't Validate Decompressed Archive Vulnerability
MODERATECVE-2026-3114 is a MODERATE (CVSS 6.5) mattermost doesn't validate decompressed archive vulnerability (CWE-409: Improper Handling of Highly Compressed Data (Data Amplification)) affecting Github.com/mattermost/mattermost/server/v8 libraries in the Go ecosystem. The issue involves mattermost doesn't validate decompressed archive entry sizes during file extraction. Remediation is available by upgrading affected packages to version 11.4.1, 11.3.2, 11.2.4, 10.11.12, 8.0.0-20260217110922-b7d4a1f1f59b.
CVE-2026-3114 at a Glance
Security Impact
CVSS: 6.5
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:N/I:N/A:H).
How to Fix CVE-2026-3114
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 11.2.4Upgrade github.com/mattermost/mattermost/server/v8 to 10.11.12Upgrade 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-2026-3114, 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-409: Improper Handling of Highly Compressed Data (Data Amplification), where the product does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a large output. 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-2026-3114 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
< 11.4.1
All 1 versions
11.4.0
|
11.4.1
|
|
github.com/mattermost/mattermost/server/v8
|
Go |
≥ 11.3.0
< 11.3.2
|
11.3.2
|
|
github.com/mattermost/mattermost/server/v8
|
Go |
≥ 11.2.0
< 11.2.4
|
11.2.4
|
|
github.com/mattermost/mattermost/server/v8
|
Go |
≥ 10.11.0
< 10.11.12
|
10.11.12
|
|
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-2026-3114?
Which Github.com/mattermost/mattermost/server/v8 versions are affected?
What version fixes CVE-2026-3114?
Is github.com/mattermost/mattermost/server/v8 affected?
What is the CVSS score of CVE-2026-3114?
What CWE is associated with CVE-2026-3114?
How can I check Go dependencies for CVE-2026-3114?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-vhgh-g7x8-4rx8",
"modified" : "2026-03-31T23:05:48Z",
"published" : "2026-03-26T18:31:42Z",
"aliases" : [ "CVE-2026-3114" ],
"summary" : "Mattermost doesn't validate decompressed archive entry sizes during file extraction",
"details" : "Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to validate decompressed archive entry sizes during file extraction which allows authenticated users with file upload permissions to cause a denial of service via crafted zip archives containing highly compressed entries (zip bombs) that exhaust server memory. Mattermost Advisory ID: MMSA-2026-00598.",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost/server/v8"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "11.4.0"
}, {
"fixed" : "11.4.1"
} ]
} ],
"versions" : [ "11.4.0" ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost/server/v8"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "11.3.0"
}, {
"fixed" : "11.3.2"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost/server/v8"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "11.2.0"
}, {
"fixed" : "11.2.4"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost/server/v8"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "10.11.0"
}, {
"fixed" : "10.11.12"
} ]
} ]
}, {
"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-2026-3114"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/mattermost/mattermost"
}, {
"type" : "WEB",
"url" : "https://mattermost.com/security-updates"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-409" ],
"severity" : "MODERATE",
"github_reviewed" : true,
"github_reviewed_at" : "2026-03-31T23:05:48Z",
"nvd_published_at" : "2026-03-26T17:16:42Z"
}
}