CVE-2026-33393 (GCVE-0-2026-33393)
Vulnerability from cvelistv5 – Published: 2026-03-19 22:04 – Updated: 2026-03-20 20:15
VLAI
EPSS
VEX
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.
Severity
4.3 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-03-20 20:15 UTC
CWE
- CWE-284 - Improper Access Control
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/discourse/discourse/security/a… | x_refsource_CONFIRM |
| https://github.com/discourse/discourse/commit/80b… | x_refsource_MISC |
| https://github.com/discourse/discourse/commit/d84… | x_refsource_MISC |
| https://github.com/discourse/discourse/commit/f99… | x_refsource_MISC |
Impacted products
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-33393",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-03-20T20:15:06.393968Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-03-20T20:15:16.294Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"product": "discourse",
"vendor": "discourse",
"versions": [
{
"status": "affected",
"version": "\u003e= 2026.1.0-latest, \u003c 2026.1.2"
},
{
"status": "affected",
"version": "\u003e= 2026.2.0-latest, \u003c 2026.2.1"
},
{
"status": "affected",
"version": "= 2026.3.0-latest"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "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."
}
],
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 4.3,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "LOW",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N",
"version": "3.1"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-284",
"description": "CWE-284: Improper Access Control",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-03-19T22:04:26.484Z",
"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"shortName": "GitHub_M"
},
"references": [
{
"name": "https://github.com/discourse/discourse/security/advisories/GHSA-95r5-p6qr-hgw6",
"tags": [
"x_refsource_CONFIRM"
],
"url": "https://github.com/discourse/discourse/security/advisories/GHSA-95r5-p6qr-hgw6"
},
{
"name": "https://github.com/discourse/discourse/commit/80b19c15fe9c7bc890d1a54f454c8446312ac6d2",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/discourse/discourse/commit/80b19c15fe9c7bc890d1a54f454c8446312ac6d2"
},
{
"name": "https://github.com/discourse/discourse/commit/d8467b9fbb3d9ed6047b4e508d3fef88a37b8a02",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/discourse/discourse/commit/d8467b9fbb3d9ed6047b4e508d3fef88a37b8a02"
},
{
"name": "https://github.com/discourse/discourse/commit/f99099cfbc6b76fe39d6fa2daa48efd69497fb8e",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/discourse/discourse/commit/f99099cfbc6b76fe39d6fa2daa48efd69497fb8e"
}
],
"source": {
"advisory": "GHSA-95r5-p6qr-hgw6",
"discovery": "UNKNOWN"
},
"title": "Discourse fixes loose hostname matching in spam host allowlist"
}
},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-33393",
"datePublished": "2026-03-19T22:04:26.484Z",
"dateReserved": "2026-03-19T17:02:34.169Z",
"dateUpdated": "2026-03-20T20:15:16.294Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-33393",
"date": "2026-09-26",
"epss": "0.00343",
"percentile": "0.25204"
},
"nvd": {
"cve": {
"affected": [
{
"affectedData": [
{
"product": "discourse",
"vendor": "discourse",
"versions": [
{
"status": "affected",
"version": "\u003e= 2026.1.0-latest, \u003c 2026.1.2"
},
{
"status": "affected",
"version": "\u003e= 2026.2.0-latest, \u003c 2026.2.1"
},
{
"status": "affected",
"version": "= 2026.3.0-latest"
}
]
}
],
"source": "security-advisories@github.com"
}
],
"configurations": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:*",
"matchCriteriaId": "4BE96625-3609-410C-B41E-4A824C1A57C0",
"versionEndExcluding": "2026.1.2",
"versionStartIncluding": "2026.1.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:*",
"matchCriteriaId": "FD31CF04-CF2F-4FB9-8880-9243BC7671A7",
"versionEndExcluding": "2026.2.1",
"versionStartIncluding": "2026.2.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:a:discourse:discourse:2026.3.0:*:*:*:latest:*:*:*",
"matchCriteriaId": "E3FE9277-4F6B-4FD0-991F-F0FB8D226E1C",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "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."
},
{
"lang": "es",
"value": "Discourse es una plataforma de discusi\u00f3n de c\u00f3digo abierto. Antes de las versiones 2026.3.0-latest.1, 2026.2.1 y 2026.1.2, la verificaci\u00f3n \u0027allowed_spam_host_domains\u0027 utilizaba \u0027String#end_with?\u0027 sin validaci\u00f3n de l\u00edmites de dominio, lo que permit\u00eda que dominios como \u0027attacker-example.com\u0027 eludieran la protecci\u00f3n contra el correo no deseado cuando \u0027example.com\u0027 estaba en lista blanca. Las versiones 2026.3.0-latest.1, 2026.2.1 y 2026.1.2 requieren una coincidencia exacta o una coincidencia de subdominio adecuada (precedida por \u0027.\u0027) para evitar la elusi\u00f3n basada en sufijos de \u0027newuser_spam_host_threshold\u0027. No hay soluciones alternativas conocidas disponibles."
}
],
"id": "CVE-2026-33393",
"lastModified": "2026-06-17T10:37:24.870",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 4.3,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "LOW",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N",
"version": "3.1"
},
"exploitabilityScore": 2.8,
"impactScore": 1.4,
"source": "security-advisories@github.com",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-33393",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-03-20T20:15:06.393968Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-03-19T22:16:42.497",
"references": [
{
"source": "security-advisories@github.com",
"tags": [
"Patch"
],
"url": "https://github.com/discourse/discourse/commit/80b19c15fe9c7bc890d1a54f454c8446312ac6d2"
},
{
"source": "security-advisories@github.com",
"tags": [
"Patch"
],
"url": "https://github.com/discourse/discourse/commit/d8467b9fbb3d9ed6047b4e508d3fef88a37b8a02"
},
{
"source": "security-advisories@github.com",
"tags": [
"Patch"
],
"url": "https://github.com/discourse/discourse/commit/f99099cfbc6b76fe39d6fa2daa48efd69497fb8e"
},
{
"source": "security-advisories@github.com",
"tags": [
"Vendor Advisory"
],
"url": "https://github.com/discourse/discourse/security/advisories/GHSA-95r5-p6qr-hgw6"
}
],
"sourceIdentifier": "security-advisories@github.com",
"vulnStatus": "Analyzed",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-284"
}
],
"source": "security-advisories@github.com",
"type": "Secondary"
}
]
}
},
"redhat_vex": {
"current_release_date": "2026-03-27T07:38:07+00:00",
"cve": "CVE-2026-33393",
"id": "CVE-2026-33393",
"initial_release_date": "2026-01-01T00:00:00+00:00",
"product_status:known_not_affected": "1",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "Discourse fixes loose hostname matching in spam host allowlist",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33393.json",
"version": "3"
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-33393",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-03-20T20:15:06.393968Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-03-20T20:15:12.725Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"product": "discourse",
"vendor": "discourse",
"versions": [
{
"status": "affected",
"version": "\u003e= 2026.1.0-latest, \u003c 2026.1.2"
},
{
"status": "affected",
"version": "\u003e= 2026.2.0-latest, \u003c 2026.2.1"
},
{
"status": "affected",
"version": "= 2026.3.0-latest"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "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."
}
],
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 4.3,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "LOW",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N",
"version": "3.1"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-284",
"description": "CWE-284: Improper Access Control",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-03-19T22:04:26.484Z",
"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"shortName": "GitHub_M"
},
"references": [
{
"name": "https://github.com/discourse/discourse/security/advisories/GHSA-95r5-p6qr-hgw6",
"tags": [
"x_refsource_CONFIRM"
],
"url": "https://github.com/discourse/discourse/security/advisories/GHSA-95r5-p6qr-hgw6"
},
{
"name": "https://github.com/discourse/discourse/commit/80b19c15fe9c7bc890d1a54f454c8446312ac6d2",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/discourse/discourse/commit/80b19c15fe9c7bc890d1a54f454c8446312ac6d2"
},
{
"name": "https://github.com/discourse/discourse/commit/d8467b9fbb3d9ed6047b4e508d3fef88a37b8a02",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/discourse/discourse/commit/d8467b9fbb3d9ed6047b4e508d3fef88a37b8a02"
},
{
"name": "https://github.com/discourse/discourse/commit/f99099cfbc6b76fe39d6fa2daa48efd69497fb8e",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/discourse/discourse/commit/f99099cfbc6b76fe39d6fa2daa48efd69497fb8e"
}
],
"source": {
"advisory": "GHSA-95r5-p6qr-hgw6",
"discovery": "UNKNOWN"
},
"title": "Discourse fixes loose hostname matching in spam host allowlist"
}
},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-33393",
"datePublished": "2026-03-19T22:04:26.484Z",
"dateReserved": "2026-03-19T17:02:34.169Z",
"dateUpdated": "2026-03-20T20:15:16.294Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
Loading…
Loading…
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Loading…
Loading…
The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Loading…
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
Loading…