Medium
Plugin bot username conflict allows user account to be used as bot identity in Mattermost Server
Type: advisorySources: OSV
Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 fail to validate that a username returned during bot registration belongs to a bot account, which allows an unprivileged attacker to intercept private messages sent by plugins via direct message channels by pre-registering a user account with a predictable plugin bot username.. Mattermost Advisory ID: MMSA-2026-00649
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-6046
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 7 Nov 2026, 06:30 UTC · Revision 1
Source evidence
Plugin bot username conflict allows user account to be used as bot identity in Mattermost Server
core-osv · Original sourcePublished 12 Jun 2026, 15:52 UTC
Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 fail to validate that a username returned during bot registration belongs to a bot account, which allows an unprivileged attacker to intercept private messages sent by plugins via direct message channels by pre-registering a user account with a predictable plugin bot username.. Mattermost Advisory ID: MMSA-2026-00649
osv:CVE-2026-6046
Complete source record
{
"id": "e2f3c5cc5a77414b99d24908133bfcda39e292e509c843bcc546eaa867c07753",
"url": "https://osv.dev/vulnerability/CVE-2026-6046",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Plugin bot username conflict allows user account to be used as bot identity in Mattermost Server",
"summary": "Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 fail to validate that a username returned during bot registration belongs to a bot account, which allows an unprivileged attacker to intercept private messages sent by plugins via direct message channels by pre-registering a user account with a predictable plugin bot username.. Mattermost Advisory ID: MMSA-2026-00649",
"evidence": "osv:CVE-2026-6046",
"products": [],
"severity": "medium",
"structured": {
"id": "CVE-2026-6046",
"aliases": [
"CVE-2026-6046",
"GHSA-3vmp-whvv-5v9v",
"GO-2026-6279"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/mattermost/mattermost",
"type": "GIT",
"events": [
{
"introduced": "5b955468ea1ea8b56c0fb10feb258a36a767d7bb"
},
{
"fixed": "202d125afa87fe39611686850fd82590c99ca344"
},
{
"introduced": "9f2616376582893035a7e3cb38b0fab648bba4e8"
},
{
"fixed": "d5f29c8ebbeb04460d16d9e2635ce50deeb78428"
},
{
"introduced": "d4f4e78835e86e2e76f76bfe797623076f5c9835"
},
{
"fixed": "1ce2484a00c9821ee19708d2c46720e4855033a9"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "10.11.0"
},
{
"fixed": "10.11.17"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "11.5.0"
},
{
"fixed": "11.5.5"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "11.6.0"
},
{
"fixed": "11.6.2"
}
],
"source": "CPE_RANGE"
}
]
}
}
],
"versions": [
"v10.11.15-rc1",
"v10.11.15",
"v11.5.4",
"v11.6.1-rc1",
"v11.6.1",
"v11.5.3",
"v10.11.14",
"v11.5.2-rc3",
"v11.5.2",
"v11.6.0",
"v10.11.14-rc1",
"v11.5.0",
"v11.5.2-rc2",
"v11.5.2-rc1",
"v10.11.13",
"v11.5.1",
"v10.11.13-rc1",
"v10.11.12",
"v10.11.11-rc2",
"v10.11.11",
"v10.11.11-rc1",
"v10.11.10",
"v10.11.9",
"v10.11.9-rc1",
"v10.11.8",
"v10.11.7",
"v10.11.6",
"v10.11.5",
"v10.11.4-rc3",
"v10.11.4",
"v10.11.4-rc2",
"v10.11.4-rc1",
"v10.11.3",
"v10.11.2-rc2",
"v10.11.2",
"v10.11.2-rc1",
"v10.11.1",
"v10.11.1-rc1",
"v10.11.0-rc3",
"v10.11.0",
"mattermost-redux@10.11.0",
"@mattermost/types@10.11.0",
"@mattermost/client@10.11.0"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-6046.json"
}
}
],
"modified": "2026-10-28T02:30:49.829635627Z",
"provider": "osv",
"references": [
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/6xxx/CVE-2026-6046.json",
"https://mattermost.com/security-updates",
"https://nvd.nist.gov/vuln/detail/CVE-2026-6046"
],
"provider_metadata": {
"cwe_ids": [
"CWE-200"
],
"cna_assigner": "Mattermost",
"unresolved_ranges": [
{
"extracted_events": [
{
"range": [
{
"introduced": "11.6.0"
},
{
"last_affected": "11.6.1"
},
{
"introduced": "11.5.0"
},
{
"last_affected": "11.5.4"
},
{
"introduced": "10.11.0"
},
{
"last_affected": "10.11.15"
},
{
"introduced": "10.11.0"
},
{
"last_affected": "10.11.16"
}
],
"source": "AFFECTED_FIELD",
"strategy": "StandardRange"
}
]
}
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/6xxx/CVE-2026-6046.json"
}
},
"related_cves": [
{
"value": "CVE-2026-6046",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 518502,
"published_at": "2026-06-12T15:52:33.505+00:00"
}