{
"id": "GHSA-cjm8-jxpw-g43m",
"aliases": [
"CVE-2026-6340"
],
"details": "Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to validate 7zip archive structure before processing which allows an authenticated attacker to cause server memory exhaustion and denial of service via uploading a specially crafted 7zip file with excessive folder declarations.. Mattermost Advisory ID: MMSA-2026-00573",
"summary": "Mattermost doesn't validate 7zip archive structure before processing",
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "11.5.0"
},
{
"fixed": "11.5.2"
}
]
}
],
"package": {
"name": "github.com/mattermost/mattermost/server/v8",
"ecosystem": "Go"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "10.11.0"
},
{
"fixed": "10.11.14"
}
]
}
],
"package": {
"name": "github.com/mattermost/mattermost/server/v8",
"ecosystem": "Go"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "11.4.0"
},
{
"fixed": "11.4.4"
}
]
}
],
"package": {
"name": "github.com/mattermost/mattermost/server/v8",
"ecosystem": "Go"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "8.0.0-20260325191733-fb11968f8798"
}
]
}
],
"package": {
"name": "github.com/mattermost/mattermost/server/v8",
"ecosystem": "Go"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "5.3.2-0.20260325191733-fb11968f8798"
}
]
}
],
"package": {
"name": "github.com/mattermost/mattermost-server",
"ecosystem": "Go"
}
}
],
"modified": "2026-06-01T15:09:30Z",
"severity": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L"
}
],
"published": "2026-05-18T09:31:47Z",
"references": [
{
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-6340",
"type": "ADVISORY"
},
{
"url": "https://github.com/mattermost/mattermost/commit/fb11968f8798925c7b75711025bc5f991124ba26",
"type": "WEB"
},
{
"url": "https://github.com/mattermost/mattermost",
"type": "PACKAGE"
},
{
"url": "https://mattermost.com/security-updates",
"type": "WEB"
}
],
"schema_version": "1.4.0",
"database_specific": {
"cwe_ids": [
"CWE-789"
],
"severity": "MODERATE",
"github_reviewed": true,
"nvd_published_at": "2026-05-18T08:16:14Z",
"github_reviewed_at": "2026-06-01T15:09:30Z"
}
}