CVE-2026-27934 in Discourse
Summary
by MITRE • 03/20/2026
Discourse is an open-source discussion platform. Versions prior to 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 have a lack of visibility checks with a user action API endpoint that results in disclosure of the title and post excerpt to unauthorized users, leading to information disclosure. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. No known workarounds are available.
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Analysis
by VulDB Data Team • 03/26/2026
The vulnerability identified as CVE-2026-27934 affects Discourse, an open-source discussion platform that serves as a collaborative forum for communities and organizations. This issue represents a critical information disclosure flaw that undermines the platform's access control mechanisms and data protection measures. The vulnerability specifically targets user action API endpoints within Discourse versions prior to the patched releases, creating a scenario where unauthorized users can gain access to sensitive content that should remain restricted to authorized personnel only. The affected versions include 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, with the patched versions containing the necessary security controls to prevent this unauthorized access. The flaw manifests when the platform fails to properly validate user permissions before exposing content metadata including post titles and excerpts, effectively bypassing the intended visibility controls that should restrict access to private or restricted forum content.
The technical nature of this vulnerability stems from insufficient input validation and access control implementation within the user action API endpoints. When users interact with the platform through these endpoints, the system should verify that the requesting user possesses appropriate authorization levels to view specific content items. However, the flaw allows attackers to exploit this missing validation step and retrieve title information and post excerpts from discussions they should not have access to. This represents a classic case of inadequate authorization checks where the system assumes all authenticated users should have access to all content, failing to consider role-based access control requirements that are fundamental to secure application design. The vulnerability operates at the API layer, making it particularly dangerous as it can be exploited programmatically without requiring direct user interaction with the graphical interface.
The operational impact of this information disclosure vulnerability extends beyond simple data exposure, creating potential risks for organizations relying on Discourse for sensitive communications and collaborative work environments. When unauthorized users can access post titles and excerpts, they gain insights into discussion topics, content themes, and potentially confidential information that may reveal organizational strategies, ongoing projects, or sensitive conversations. This type of exposure can lead to competitive disadvantages for businesses, privacy violations for users, and potential security risks when the disclosed information includes references to internal processes or systems. The vulnerability particularly affects organizations using Discourse for internal communications, customer support forums, or communities where content confidentiality is paramount. The lack of available workarounds means that organizations cannot implement temporary fixes while planning their upgrade schedules, creating an urgent security concern that requires immediate attention.
Organizations should prioritize upgrading to the patched versions of Discourse to address this vulnerability, as there are no known workarounds that can effectively mitigate the risk without disrupting platform functionality. The patch addresses the core authorization flaw by implementing proper visibility checks that ensure only users with appropriate permissions can access content metadata through the affected API endpoints. Security teams should conduct thorough assessments of their Discourse installations to identify all affected versions and implement the necessary upgrades across their infrastructure. This vulnerability aligns with CWE-284, which describes improper access control, and represents a clear violation of the principle of least privilege that should govern all access control implementations. From an ATT&CK framework perspective, this vulnerability could be categorized under privilege escalation and credential access tactics, as it allows unauthorized users to gain information about restricted content that they would not normally be able to access, potentially enabling further exploitation attempts. The remediation process should include comprehensive testing to ensure that the patch does not introduce compatibility issues with existing forum configurations or custom integrations.