CVE-2026-49256 in Discourse
Summary
by MITRE • 07/10/2026
Discourse is an open-source discussion platform. Prior to 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5, restricted tag and tag-group names attached to publicly readable categories as allowed_tags, allowed_tag_groups, or required tag groups could leak to anonymous and unauthorized users through category and group endpoints. This issue is fixed in versions 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5.
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Analysis
by VulDB Data Team • 07/10/2026
This vulnerability affects Discourse, a popular open-source discussion platform, where sensitive tag and tag-group information was being exposed to unauthorized users through API endpoints. The flaw existed in versions prior to 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5, creating a significant information disclosure risk that could compromise the platform's content organization security model. The vulnerability specifically impacted publicly readable categories where administrators had configured restricted tag names through allowed_tags, allowed_tag_groups, or required tag groups parameters.
The technical implementation flaw stemmed from insufficient access control validation within the category and group endpoints of the Discourse application. When these endpoints were queried by anonymous or unauthorized users, they inadvertently returned information about restricted tags and tag groups that should have been hidden from users without proper authorization levels. This occurred because the platform failed to properly verify user permissions before exposing metadata related to content categorization systems. The vulnerability represents a classic case of insufficient authorization checks where the system did not adequately distinguish between public and private tag information based on user access levels.
The operational impact of this vulnerability is substantial as it allows attackers to gather intelligence about the platform's content organization structure without authentication. Anonymous users could potentially discover sensitive tagging patterns, which might reveal internal categorization strategies, content types, or organizational structures that should remain private. This information disclosure could enable more sophisticated attacks such as targeted content manipulation, social engineering campaigns, or analysis of community behavior patterns. The exposure of tag groups and their associated restrictions could also provide attackers with insights into the platform's moderation policies and content governance approaches.
From a cybersecurity perspective, this vulnerability aligns with CWE-200 (Information Exposure) and CWE-668 (Poor Access Control) categories, representing both information leakage and inadequate access control mechanisms. The issue also maps to ATT&CK technique T1592 (Gather Victim Network Information) as it enables adversaries to collect network-related data about the platform's structure and organization. Organizations using Discourse should immediately implement the patched versions 2026.6.0, 2026.5.1, 2026.4.2, or 2026.1.5 to remediate this exposure. Additionally, security teams should review their current tag and group configurations to ensure that sensitive categorization information is not inadvertently exposed through other API endpoints and consider implementing additional monitoring for unauthorized access attempts to content organization metadata. The fix addresses the root cause by enforcing proper access control validation before returning restricted tag information through category and group API responses.