Medium
Server panic via outgoing webhook responses
Type: advisorySources: OSV
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to filter nil elements from outgoing webhook attachment payloads before processing, which allows an authenticated user to cause a denial of service (server process termination) via a crafted webhook callback response containing a null attachment entry.. Mattermost Advisory ID: MMSA-2026-00641
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-4915
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 3 Nov 2026, 15:24 UTC · Revision 1
Source evidence
Server panic via outgoing webhook responses
core-osv · Original sourcePublished 25 May 2026, 07:10 UTC
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to filter nil elements from outgoing webhook attachment payloads before processing, which allows an authenticated user to cause a denial of service (server process termination) via a crafted webhook callback response containing a null attachment entry.. Mattermost Advisory ID: MMSA-2026-00641
osv:CVE-2026-4915
Complete source record
{
"id": "af8786340044a7a7f54c76e68307dc329f4961bb693fdebe6f10b760b8afe962",
"url": "https://osv.dev/vulnerability/CVE-2026-4915",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Server panic via outgoing webhook responses",
"summary": "Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to filter nil elements from outgoing webhook attachment payloads before processing, which allows an authenticated user to cause a denial of service (server process termination) via a crafted webhook callback response containing a null attachment entry.. Mattermost Advisory ID: MMSA-2026-00641",
"evidence": "osv:CVE-2026-4915",
"products": [],
"severity": "medium",
"structured": {
"id": "CVE-2026-4915",
"aliases": [
"CVE-2026-4915",
"GHSA-5gmf-x7hg-97wf",
"GO-2026-5845"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/mattermost/mattermost",
"type": "GIT",
"events": [
{
"introduced": "5b955468ea1ea8b56c0fb10feb258a36a767d7bb"
},
{
"fixed": "f6760151c4a7b4b9d0807fa18892aaf24a3e190e"
},
{
"introduced": "2a1ac98bd3fae587927adf9340ba266c8c02018e"
},
{
"fixed": "292d4b7ea15b49a29989129758f25be37aec946e"
},
{
"introduced": "9f2616376582893035a7e3cb38b0fab648bba4e8"
},
{
"fixed": "fff6ab3a5851dc47c65bd636281f5c678fe9de25"
},
{
"introduced": "d4f4e78835e86e2e76f76bfe797623076f5c9835"
},
{
"fixed": "ffee10a61081dcc058f92fe65ba138804c3ca73b"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "10.11.0"
},
{
"fixed": "10.11.15"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "11.4.0"
},
{
"fixed": "11.4.5"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "11.5.0"
},
{
"fixed": "11.5.4"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "11.6.0"
},
{
"fixed": "11.6.1"
}
],
"source": "CPE_RANGE"
}
]
}
}
],
"versions": [
"v11.5.3",
"v10.11.14",
"v11.4.4",
"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",
"v11.4.3",
"v10.11.13",
"v11.5.1",
"v10.11.13-rc1",
"v11.4.2",
"v10.11.12",
"v11.4.1-rc2",
"v11.4.1-rc1",
"v11.4.1",
"v10.11.11-rc2",
"v10.11.11",
"v11.4.0-rc3",
"v11.4.0",
"mattermost-redux@11.4.0",
"@mattermost/types@11.4.0",
"@mattermost/client@11.4.0",
"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-2026-4915.json"
}
}
],
"modified": "2026-10-28T02:30:29.748938965Z",
"provider": "osv",
"references": [
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/4xxx/CVE-2026-4915.json",
"https://mattermost.com/security-updates",
"https://nvd.nist.gov/vuln/detail/CVE-2026-4915"
],
"provider_metadata": {
"cwe_ids": [
"CWE-754"
],
"cna_assigner": "Mattermost",
"unresolved_ranges": [
{
"extracted_events": [
{
"range": [
{
"introduced": "11.6.0"
},
{
"last_affected": "11.6.0"
}
],
"source": "AFFECTED_FIELD",
"strategy": "StandaloneSingleVersion"
}
]
},
{
"extracted_events": [
{
"range": [
{
"introduced": "11.5.0"
},
{
"last_affected": "11.5.3"
},
{
"introduced": "11.4.0"
},
{
"last_affected": "11.4.4"
},
{
"introduced": "10.11.0"
},
{
"last_affected": "10.11.14"
}
],
"source": "AFFECTED_FIELD",
"strategy": "StandardRange"
}
]
}
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/4xxx/CVE-2026-4915.json"
}
},
"related_cves": [
{
"value": "CVE-2026-4915",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 496795,
"published_at": "2026-05-25T07:10:23.254+00:00"
}