> CVE-2026-31869 [MEDIUM]

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PUBLISHED
2026-03-20 03:15
MODIFIED
2026-03-20 03:15
CVSS_SCORE V3
5.3
EPSS (Prob. Exploit)
0.19%
Top 91.3%
DATA SOURCES:
NVD 🔗 2026-03-20 CWE MITRE 🔗 2026-11-01 FIRST EPSS 🔗 2026-11-08 OSV 🔗 2026-11-08

> DESCRIPTION

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.

> AFFECTED_PRODUCTS

ℹ️ Aucun produit affecté n'a encore été publié par NVD pour cette CVE.

> CVSS V3 METRICS

CVSS_VECTOR
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

> MÉTRIQUES CVSS DÉTAILLÉES

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Métrique Valeur Interprétation
AV (Vecteur d'Attaque)
Attack Vector
Network (N)
Exploit possible à distance via réseau (HTTP, API, etc.)
AC (Complexité d'Attaque)
Attack Complexity
Low (L)
Peu de conditions requises pour exploiter
PR (Privilèges Requis)
Privileges Required
Low (L)
Authentifié avec compte utilisateur basique
UI (Interaction Utilisateur)
User Interaction
None (N)
Aucune interaction utilisateur nécessaire
S (Périmètre)
Scope
Unchanged (U)
Impact reste dans le périmètre du composant compromis
C (Impact Confidentialité)
Confidentiality Impact
Low (L)
Divulgation limitée d'informations
I (Impact Intégrité)
Integrity Impact
None (N)
Aucune modification de données possible
A (Impact Disponibilité)
Availability Impact
None (N)
Aucune interruption de service

> RÉSUMÉ DES IMPACTS

Confidentialité
Low
Divulgation limitée d'informations
Intégrité
None
Aucune modification de données possible
Disponibilité
None
Aucune interruption de service

> WEAKNESSES

CWE-200 CWE-285 CWE-639

> CWE DETAILED DESCRIPTIONS

CWE-200: Exposure of Sensitive Information to an Unauthorized Actor - The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. | CWE-285: Improper Authorization - The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. | CWE-639: Authorization Bypass Through User-Controlled Key - The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.

> OSV (GOOGLE OPEN SOURCE VULNERABILITIES)

Discourse: Composer mentions endpoint leaks hidden group membership through PM `allowed_names` check

AFFECTED PACKAGES:
Unknown / Unknown
10 versions affected
ALIASES:
BIT-discourse-2026-31869, GHSA-5f9h-vp7v-7vq5

> HISTORIQUE DES MODIFICATIONS

Première apparition
20/03/2026 03:15
Source: NVD
📊 ENRICHISSEMENT 01/04/2026 06:02
CWE
Champ modifié: Description CWE
Ancienne valeur:
N/A
Nouvelle valeur:
CWE-200: Exposure of Sensitive Information to an Unauthorized Actor - The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. | CWE-...
Total des modifications: 1 Dernière mise à jour: 7 months ago

> REFERENCES

https://github.com/discourse/discourse/security/advisories/GHSA-5f9h-vp7v-7vq5
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