CVE-2026-31869

Published: Mar 20, 2026 Last Modified: Mar 20, 2026
ExploitDB:
Other exploit source:
Google Dorks:
MEDIUM 5,3
Source: [email protected]
Attack Vector: network
Attack Complexity: low
Privileges Required: low
User Interaction: none
Confidentiality: N/A
Integrity: N/A
Availability: N/A

Description

AI Translation Available

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.

200

Exposure of Sensitive Information to an Unauthorized Actor

Draft
Abstraction: Class Structure: Simple
Common Consequences
Security Scopes Affected:
Confidentiality
Potential Impacts:
Read Application Data
Applicable Platforms
Technologies: Mobile, Not Technology-Specific, Web Based
Likelihood of Exploit: High
View CWE Details
285

Improper Authorization

Draft
Abstraction: Class Structure: Simple
Common Consequences
Security Scopes Affected:
Confidentiality Integrity Access Control
Potential Impacts:
Read Application Data Read Files Or Directories Modify Application Data Modify Files Or Directories Gain Privileges Or Assume Identity Execute Unauthorized Code Or Commands
Applicable Platforms
Technologies: Database Server, Not Technology-Specific, Web Server
Likelihood of Exploit: High
View CWE Details
639

Authorization Bypass Through User-Controlled Key

Incomplete
Abstraction: Base Structure: Simple
Common Consequences
Security Scopes Affected:
Access Control
Potential Impacts:
Bypass Protection Mechanism Gain Privileges Or Assume Identity
Applicable Platforms
All platforms may be affected
Likelihood of Exploit: High
View CWE Details
https://github.com/discourse/discourse/security/advisories/…
https://github.com/discourse/discourse/security/advisories/GHSA-5f9h-vp7v-7vq5