FKIE_CVE-2026-31869

Vulnerability from fkie_nvd - Published: 2026-03-20 03:15 - Updated: 2026-03-24 20:22
Severity ?
4.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/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 ComposerController#mentions endpoint reveals hidden group membership to any authenticated user who can message the group. By supplying allowed_names referencing a hidden-membership group and probing arbitrary usernames, an attacker can infer membership based on whether user_reasons returns "private" for a given user. This bypasses group member-visibility controls. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. To work around this issue, restrict the messageable policy of any hidden-membership group to staff or group members only, so untrusted users cannot reach the vulnerable code path.
References
security-advisories@github.comhttps://github.com/discourse/discourse/security/advisories/GHSA-5f9h-vp7v-7vq5Mitigation, Vendor Advisory
Impacted products
Vendor Product Version
discourse discourse *
discourse discourse *
discourse discourse 2026.3.0
To clipboard 

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              "matchCriteriaId": "4BE96625-3609-410C-B41E-4A824C1A57C0",
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  "cveTags": [],
  "descriptions": [
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      "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 ComposerController#mentions endpoint reveals hidden group membership to any authenticated user who can message the group. By supplying allowed_names referencing a hidden-membership group and probing arbitrary usernames, an attacker can infer membership based on whether user_reasons returns \"private\" for a given user. This bypasses group member-visibility controls. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. To work around this issue, restrict the messageable policy of any hidden-membership group to staff or group members only, so untrusted users cannot reach the vulnerable code path."
    },
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      "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, el endpoint ComposerController#mentions revela la membres\u00eda oculta de un grupo a cualquier usuario autenticado que puede enviar mensajes al grupo. Al proporcionar allowed_names que hacen referencia a un grupo de membres\u00eda oculta y al sondear nombres de usuario arbitrarios, un atacante puede inferir la membres\u00eda bas\u00e1ndose en si user_reasons devuelve \u0027private\u0027 para un usuario dado. Esto elude los controles de visibilidad de miembros del grupo. Las versiones 2026.3.0-latest.1, 2026.2.1 y 2026.1.2 contienen un parche. Para solucionar este problema, restrinja la pol\u00edtica de mensajer\u00eda de cualquier grupo de membres\u00eda oculta solo al personal o a los miembros del grupo, para que los usuarios no confiables no puedan alcanzar la ruta de c\u00f3digo vulnerable."
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  "id": "CVE-2026-31869",
  "lastModified": "2026-03-24T20:22:46.050",
  "metrics": {
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          "confidentialityImpact": "LOW",
          "integrityImpact": "NONE",
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          "Recovery": "NOT_DEFINED",
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          "availabilityRequirement": "NOT_DEFINED",
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          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "LOW",
          "providerUrgency": "NOT_DEFINED",
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          "valueDensity": "NOT_DEFINED",
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  "published": "2026-03-20T03:15:59.533",
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      "tags": [
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          "value": "CWE-200"
        },
        {
          "lang": "en",
          "value": "CWE-285"
        },
        {
          "lang": "en",
          "value": "CWE-639"
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      "source": "security-advisories@github.com",
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}


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  • 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.
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Detection rules are retrieved from Rulezet.