Medium
Denial of Service via HTTP/2 single packet attack on login endpoint
Type: advisorySources: OSV
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 rate limit login requests which allows unauthenticated remote attackers to cause denial of service (server crash and restart) via HTTP/2 single packet attack with 100+ parallel login requests.. Mattermost Advisory ID: MMSA-2025-00566
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-26233
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 5 Nov 2026, 01:52 UTC · Revision 1
Source evidence
Denial of Service via HTTP/2 single packet attack on login endpoint
core-osv · Original sourcePublished 25 Mar 2026, 16:24 UTC
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 rate limit login requests which allows unauthenticated remote attackers to cause denial of service (server crash and restart) via HTTP/2 single packet attack with 100+ parallel login requests.. Mattermost Advisory ID: MMSA-2025-00566
osv:CVE-2026-26233
Complete source record
{
"id": "5cc13c2692553d214533e344cde33664fa4942d38fefae1fc21b40f79d5aee9d",
"url": "https://osv.dev/vulnerability/CVE-2026-26233",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Denial of Service via HTTP/2 single packet attack on login endpoint",
"summary": "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 rate limit login requests which allows unauthenticated remote attackers to cause denial of service (server crash and restart) via HTTP/2 single packet attack with 100+ parallel login requests.. Mattermost Advisory ID: MMSA-2025-00566",
"evidence": "osv:CVE-2026-26233",
"products": [],
"severity": "medium",
"structured": {
"id": "CVE-2026-26233",
"aliases": [
"CVE-2026-26233",
"GHSA-247x-7qw8-fp98",
"GO-2026-4916"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/mattermost/mattermost",
"type": "GIT",
"events": [
{
"introduced": "5b955468ea1ea8b56c0fb10feb258a36a767d7bb"
},
{
"fixed": "e1a78d1e9111eb77008014c8fec345708c74e756"
},
{
"introduced": "ab7b138824c61fe1fe815243d7e2a914dec49c8b"
},
{
"fixed": "eda9f2a1fe66177a6dd6e96d8294e50f9bf4228d"
},
{
"introduced": "d27a2195068ddfa3ce17cf470f9739e4edb94b83"
},
{
"fixed": "b7d4a1f1f59b645a7598181d33cfc537ea9a6c9c"
},
{
"introduced": "2a1ac98bd3fae587927adf9340ba266c8c02018e"
},
{
"fixed": "84f62bb0c14a45a200af7f4dbe7186915865495f"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "10.11.0"
},
{
"fixed": "10.11.12"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "11.2.0"
},
{
"fixed": "11.2.4"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "11.3.0"
},
{
"fixed": "11.3.2"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "11.4.0"
},
{
"fixed": "11.4.1"
}
],
"source": "CPE_RANGE"
}
]
}
}
],
"versions": [
"v11.3.1",
"v11.2.3",
"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",
"v11.3.1-rc1",
"v10.11.10",
"v11.2.2",
"v11.3.0-rc4",
"v11.3.0-rc3",
"v11.3.0",
"mattermost-redux@11.3.0",
"@mattermost/types@11.3.0",
"@mattermost/client@11.3.0",
"v10.11.9",
"v11.2.1",
"v11.2.1-rc1",
"v11.2.0",
"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-2026-26233.json"
}
}
],
"modified": "2026-10-28T02:30:41.561025478Z",
"provider": "osv",
"references": [
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/26xxx/CVE-2026-26233.json",
"https://mattermost.com/security-updates",
"https://nvd.nist.gov/vuln/detail/CVE-2026-26233"
],
"provider_metadata": {
"cwe_ids": [
"CWE-400"
],
"cna_assigner": "Mattermost",
"unresolved_ranges": [
{
"extracted_events": [
{
"range": [
{
"introduced": "11.4.0"
},
{
"last_affected": "11.4.0"
}
],
"source": "AFFECTED_FIELD",
"strategy": "StandaloneSingleVersion"
}
]
},
{
"extracted_events": [
{
"range": [
{
"introduced": "11.3.0"
},
{
"last_affected": "11.3.1"
},
{
"introduced": "11.2.0"
},
{
"last_affected": "11.2.3"
},
{
"introduced": "10.11.0"
},
{
"last_affected": "10.11.11"
}
],
"source": "AFFECTED_FIELD",
"strategy": "StandardRange"
}
]
}
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/26xxx/CVE-2026-26233.json"
}
},
"related_cves": [
{
"value": "CVE-2026-26233",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 509238,
"published_at": "2026-03-25T16:24:47.694+00:00"
}