Discourse fixes loose hostname matching in spam host allowlist
Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, the `allowed_spam_host_domains` check used `String#end_with?` without domain boundary validation, allowing domains like `attacker-example.com` to bypass spam protection when `example.com` was allowlisted. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 require exact match or proper subdomain match (preceded by `.`) to prevent suffix-based bypass of `newuser_spam_host_threshold`. No known workarounds are available.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-33393
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 3 Nov 2026, 02:15 UTC · Revision 1
Source evidence
Discourse fixes loose hostname matching in spam host allowlist
core-osv · Original sourcePublished 19 Mar 2026, 22:04 UTC
Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, the `allowed_spam_host_domains` check used `String#end_with?` without domain boundary validation, allowing domains like `attacker-example.com` to bypass spam protection when `example.com` was allowlisted. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 require exact match or proper subdomain match (preceded by `.`) to prevent suffix-based bypass of `newuser_spam_host_threshold`. No known workarounds are available.
osv:CVE-2026-33393
Complete source record
{
"id": "e5f5366acfdc4936b16a11ecff3b8560853a6eb538810ec556123fc06b0a803e",
"url": "https://osv.dev/vulnerability/CVE-2026-33393",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Discourse fixes loose hostname matching in spam host allowlist",
"summary": "Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, the `allowed_spam_host_domains` check used `String#end_with?` without domain boundary validation, allowing domains like `attacker-example.com` to bypass spam protection when `example.com` was allowlisted. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 require exact match or proper subdomain match (preceded by `.`) to prevent suffix-based bypass of `newuser_spam_host_threshold`. No known workarounds are available.",
"evidence": "osv:CVE-2026-33393",
"products": [],
"severity": "medium",
"structured": {
"id": "CVE-2026-33393",
"aliases": [
"BIT-discourse-2026-33393",
"CVE-2026-33393",
"GHSA-95r5-p6qr-hgw6"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/discourse/discourse",
"type": "GIT",
"events": [
{
"introduced": "322d3c0ac6a8f133b3f82875e9dbbe310f638c1b"
},
{
"fixed": "808b2ac23d8ff421563b40203091026732471c60"
},
{
"introduced": "f7cec86997edc21d6074ceb7666f7e2e6e1b1fdf"
},
{
"fixed": "f38464e46df1b8c51f7d60826502476908d6bb2b"
},
{
"introduced": "896e810e1b296478bba91559a8fc89a9926f11fe"
},
{
"fixed": "80b19c15fe9c7bc890d1a54f454c8446312ac6d2"
},
{
"fixed": "d8467b9fbb3d9ed6047b4e508d3fef88a37b8a02"
},
{
"fixed": "f99099cfbc6b76fe39d6fa2daa48efd69497fb8e"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "2026.1.0"
},
{
"fixed": "2026.1.2"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "2026.2.0"
},
{
"fixed": "2026.2.1"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:discourse:discourse:2026.3.0:*:*:*:latest:*:*:*",
"range": [
{
"introduced": "2026.3.0"
},
{
"last_affected": "2026.3.0"
}
],
"source": "CPE_STRING"
},
{
"range": [
{
"fixed": "80b19c15fe9c7bc890d1a54f454c8446312ac6d2"
}
],
"source": "REFERENCES_COMMIT"
},
{
"range": [
{
"fixed": "d8467b9fbb3d9ed6047b4e508d3fef88a37b8a02"
}
],
"source": "REFERENCES_COMMIT"
},
{
"range": [
{
"fixed": "f99099cfbc6b76fe39d6fa2daa48efd69497fb8e"
}
],
"source": "REFERENCES_COMMIT"
}
]
}
}
],
"versions": [
"2026.3.0",
"= 2026.3.0-latest",
"v2026.1.1",
"v2026.2.0",
"v2026.3.0-latest",
"v2026.1.0",
"stable",
"esr",
"v2026.2.0-latest",
"v2026.1.0-latest"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-33393.json"
}
}
],
"modified": "2026-10-28T02:30:25.312364126Z",
"provider": "osv",
"references": [
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33393.json",
"https://github.com/discourse/discourse/security/advisories/GHSA-95r5-p6qr-hgw6",
"https://nvd.nist.gov/vuln/detail/CVE-2026-33393",
"https://github.com/discourse/discourse/commit/80b19c15fe9c7bc890d1a54f454c8446312ac6d2",
"https://github.com/discourse/discourse/commit/d8467b9fbb3d9ed6047b4e508d3fef88a37b8a02",
"https://github.com/discourse/discourse/commit/f99099cfbc6b76fe39d6fa2daa48efd69497fb8e"
],
"provider_metadata": {
"cwe_ids": [
"CWE-284"
],
"cna_assigner": "GitHub_M",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33393.json"
}
},
"related_cves": [
{
"value": "CVE-2026-33393",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 491829,
"published_at": "2026-03-19T22:04:26.484+00:00"
}