FKIE_CVE-2026-33393

Vulnerability from fkie_nvd - Published: 2026-03-19 22:16 - Updated: 2026-03-24 20:41
Severity ?
4.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
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.
References
security-advisories@github.comhttps://github.com/discourse/discourse/commit/80b19c15fe9c7bc890d1a54f454c8446312ac6d2Patch
security-advisories@github.comhttps://github.com/discourse/discourse/commit/d8467b9fbb3d9ed6047b4e508d3fef88a37b8a02Patch
security-advisories@github.comhttps://github.com/discourse/discourse/commit/f99099cfbc6b76fe39d6fa2daa48efd69497fb8ePatch
security-advisories@github.comhttps://github.com/discourse/discourse/security/advisories/GHSA-95r5-p6qr-hgw6Vendor Advisory
Impacted products
Vendor Product Version
discourse discourse *
discourse discourse *
discourse discourse 2026.3.0
To clipboard 

{
  "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": "2026-03-24T20:41:57.427",
  "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"
      }
    ]
  },
  "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": "Primary"
    }
  ]
}


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Taxonomy of the tags.




Sightings

Author Source Type Date

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.



Detection rules are retrieved from Rulezet.