CVE-2024-53991 Scanner

Discourse is a popular open-source forum software used by communities around the world for facilitating discussions and information sharing. Developed to enhance community interaction, it is frequently utilized by businesses, educational institutions, and online communities. Its capabilities extend to facilitating structured discussions, content moderation, and user management, making it versatile for varied discussion requirements. Discourse instances can be deployed on both personal and organizational servers, offering flexibility in hosting environments. The platform's user-friendly interface and robust customization options make it a preferred choice for many organizations. As an open-source project, it benefits from a collaborative development approach, ensuring continuous updates and feature enhancements.

This vulnerability impacts Discourse instances that store uploads and backups locally on disk using the `FileStore--LocalStore` configuration. An attacker can exploit this vulnerability if they can guess the name of a backup file, potentially tricking nginx into serving sensitive backup files. This flaw arises from an improper handling within the nginx configuration, allowing unauthorized access to backup files. Such access could lead to significant data exposure if not adequately addressed. A successful exploit doesn't require user interaction, increasing the risk factor associated with this vulnerability. It's crucial for administrators to evaluate their Discourse configurations to mitigate potential risks.

The vulnerability surfaces due to a misconfiguration in the nginx settings of Discourse instances using local storage for backups. An attacker needs specific knowledge about backup file names to craft a request that makes nginx send the backup file unintentionally. This involves manipulating HTTP requests to include parameters that bypass standard access controls. The flaw specifically interacts with nginx's processing of certain headers and URL mappings, exploiting a lack of adequate validation and filtering. The endpoint vulnerable to this flaw relies on predictable naming conventions for backup files, which an attacker could leverage. Properly crafting requests using specific headers and URL structures forms the technical basis for exploitation.

If an attacker successfully exploits this vulnerability, they could gain unauthorized access to sensitive backup files stored on affected Discourse instances. This access might include sensitive user data, discussion content, and potentially even configuration files. Disclosure of such information can lead to further security threats, such as identity theft, privacy violations, and escalation of attacks leveraging disclosed information. Organizations might face reputational damage, legal implications, and a breach of trust with their user base. Rapid identification and addressing of this vulnerability are vital to prevent data breaches and ensure the security of user data.

REFERENCES

• https://projectdiscovery.io/blog/discourse-backup-disclosure-rails-send_file-quirk/
• https://github.com/discourse/discourse/security/advisories/GHSA-567m-82f6-56rv