CVE-2024-56197 in Discourse
Summary
by MITRE • 02/04/2025
Discourse is an open source platform for community discussion. PM titles and metadata can be read by other users when the "PM tags allowed for groups" option is enabled, the other user is a member of a group added to this option, and the PM has been tagged. This issue has been patched in the latest `stable`, `beta` and `tests-passed` versions of Discourse. Users are advised to upgrade. Users unable to upgrade should remove all groups from the the "PM tags allowed for groups" option.
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Analysis
by VulDB Data Team • 02/05/2025
CVE-2024-56197 represents a privilege escalation vulnerability within the Discourse open source community discussion platform that exposes private message metadata to unauthorized users. This vulnerability specifically targets the platform's permission model when the "PM tags allowed for groups" configuration option is enabled, creating a scenario where users can access metadata from private messages they should not be authorized to view. The flaw exists at the application logic level where the system fails to properly enforce access controls between private messages and user group memberships.
The technical implementation of this vulnerability stems from inadequate authorization checks within Discourse's private messaging system. When administrators configure the "PM tags allowed for groups" option, they specify which user groups can apply tags to private messages. However, the platform's access control mechanism does not properly validate whether the recipient of a private message belongs to any of the groups that have been granted permission to tag messages. This creates a situation where users who are members of tagged groups can potentially read the titles and metadata of private messages that have been tagged, even if they are not the intended recipients of those messages. The vulnerability manifests when multiple conditions are met simultaneously: the PM tags option is enabled, the user belongs to an approved group, and the private message has been tagged.
The operational impact of CVE-2024-56197 extends beyond simple information disclosure, as it undermines the fundamental privacy guarantees that private messaging systems are designed to provide. Attackers who identify their target user groups can exploit this vulnerability to gain unauthorized access to sensitive metadata from private conversations, potentially including user intentions, topics of discussion, and communication patterns. This exposure could enable social engineering attacks, information gathering for targeted phishing campaigns, or simply violate user privacy expectations. The vulnerability aligns with CWE-284, which describes improper access control in software systems, and represents a clear violation of the principle of least privilege that should govern all access control decisions within secure applications.
This vulnerability is particularly concerning within the context of the ATT&CK framework as it maps to the privilege escalation and credential access tactics. An attacker who identifies that a target user belongs to a group that has been granted PM tagging permissions could systematically enumerate private message metadata to build profiles of users and their communication patterns. The impact is exacerbated by the fact that this vulnerability affects the core messaging functionality of a community platform, potentially compromising the trust users place in the system's privacy controls. Organizations using Discourse must consider this vulnerability as part of their broader security posture assessment, particularly in environments where sensitive communications are expected to remain private.
The remediation approach recommended by the Discourse team involves upgrading to the latest stable, beta, or tests-passed versions where the vulnerability has been patched. This upgrade addresses the underlying access control logic that was permitting unauthorized metadata access. For organizations unable to perform immediate upgrades, the suggested mitigation is to remove all groups from the "PM tags allowed for groups" configuration option, effectively disabling the problematic feature until a proper upgrade can be completed. This approach aligns with the principle of least privilege by reducing the attack surface and limiting the scope of potential unauthorized access. The vulnerability demonstrates the importance of proper access control implementation and the need for comprehensive testing of permission models in multi-user collaborative platforms. Organizations should also consider implementing additional monitoring to detect unusual patterns of private message metadata access that could indicate exploitation attempts.