CVE-2023-49099 in Discourse
Summary
by MITRE • 01/12/2024
Discourse is a platform for community discussion. Under very specific circumstances, secure upload URLs associated with posts can be accessed by guest users even when login is required. This vulnerability has been patched in 3.2.0.beta4 and 3.1.4.
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Analysis
by VulDB Data Team • 02/03/2024
The vulnerability identified as CVE-2023-49099 affects Discourse, a popular platform designed for community discussion and collaboration. This issue represents a critical access control flaw that undermines the security model of the platform by allowing unauthorized guest users to access secure upload resources that should be restricted to authenticated users only. The vulnerability specifically manifests when certain conditions are met within the platform's upload handling mechanisms, creating an unexpected pathway for privilege escalation through unauthorized resource access.
The technical flaw stems from improper authorization checks within the upload URL generation and validation process. When posts contain uploaded files, the system generates secure URLs that should require authentication to access. However, under specific circumstances involving the interaction between post visibility settings, user authentication states, and URL expiration handling, guest users can bypass these security controls. This represents a classic authorization bypass vulnerability that falls under the CWE-285 category of improper authorization. The vulnerability exploits the platform's expectation that authenticated sessions will properly maintain access controls, but fails to account for edge cases in session management and resource access validation.
The operational impact of this vulnerability extends beyond simple unauthorized file access, potentially exposing sensitive information shared within community discussions. Guest users who can access these secure uploads may gain access to confidential documents, personal information, or proprietary content that was intended to remain private to authenticated community members. This compromises the platform's data protection mechanisms and could lead to privacy violations, intellectual property exposure, or other security incidents depending on the nature of the uploaded content. The vulnerability particularly affects organizations that rely on Discourse for sensitive communications or collaborative work environments where access control is paramount.
Mitigation strategies should focus on immediate deployment of the patched versions 3.2.0.beta4 and 3.1.4, which contain the necessary fixes for the authorization bypass. Administrators should conduct thorough security reviews of their Discourse installations to ensure proper patching across all environments. Additionally, organizations should implement monitoring for unauthorized access attempts to upload resources and consider implementing additional access logging to detect potential exploitation attempts. The vulnerability demonstrates the importance of comprehensive testing for edge cases in access control systems and aligns with ATT&CK technique T1078 for valid accounts and privilege escalation through unauthorized resource access. Organizations should also review their broader security posture to ensure that similar authorization bypass vulnerabilities do not exist in other components of their infrastructure that handle user-specific resources.