CVE-2026-21865
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2026-01-28

Last updated on: 2026-01-30

Assigner: GitHub, Inc.

Description
Discourse is an open source discussion platform. In versions prior to 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0, moderators can convert some personal messages to public topics when they shouldn't have access. This issue is patched in versions 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0. As a workaround, site admin can temporarily revoke the moderation role from untrusted moderators or remove the moderator group from the "personal message enabled groups" site setting until the Discourse instance has been upgraded to a version that has been patched.
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Meta Information
Published
2026-01-28
Last Modified
2026-01-30
Generated
2026-06-16
AI Q&A
2026-01-29
EPSS Evaluated
2026-06-15
NVD
CVE-2026-21865
EUVD
EUVD-2026-4874
Affected Vendors & Products
Showing 4 associated CPEs
Vendor Product Version / Range
discourse discourse to 3.5.4 (exc)
discourse discourse From 2025.11.0 (inc) to 2025.11.2 (exc)
discourse discourse 2025.12.0
discourse discourse 2026.1.0
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-862 The product does not perform an authorization check when an actor attempts to access a resource or perform an action.
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Executive Summary

This vulnerability in Discourse allows moderators to convert some personal messages into public topics even when they should not have the access to do so. This means that private communications can be exposed publicly by moderators due to improper access controls in versions prior to 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0.

Impact Analysis

The vulnerability can lead to unauthorized disclosure of private messages, compromising user privacy and confidentiality. This could damage trust in the platform, expose sensitive information, and potentially lead to reputational harm or legal consequences for the site operators.

Mitigation Strategies

Site administrators should temporarily revoke the moderation role from untrusted moderators or remove the moderator group from the "personal message enabled groups" site setting until the Discourse instance is upgraded to a patched version (3.5.4, 2025.11.2, 2025.12.1, or 2026.1.0).

Compliance Impact

This vulnerability allows moderators to convert personal messages to public topics without proper access, potentially exposing private or sensitive information. Such unauthorized disclosure could lead to non-compliance with data protection regulations like GDPR and HIPAA, which require safeguarding personal and sensitive data from unauthorized access or exposure.

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