Executive Summary

CVE-2026-30231 is an Insecure Direct Object Reference (IDOR) vulnerability in the FlintSH/Flare file sharing platform versions prior to 1.7.2. The issue exists in the raw and direct file access endpoints, which only block unauthenticated users from accessing private files. However, any authenticated user who knows the file URL can access private files even if they are not the owner or an admin.

This happens because these endpoints check only if a user is authenticated, not whether the user owns the file or has administrative privileges. This is inconsistent with other endpoints like download and thumbnail routes, which enforce stricter access controls.

The vulnerability allows unauthorized disclosure of confidential private files to any authenticated user who can guess or obtain the file URL.

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Impact Analysis

[{'type': 'paragraph', 'content': 'This vulnerability can lead to unauthorized access to private files by any authenticated user, even if they do not own the files or have administrative rights.'}, {'type': 'paragraph', 'content': 'As a result, confidential or sensitive information stored in private files could be exposed to unauthorized users, potentially leading to data breaches or leakage of sensitive information.'}, {'type': 'paragraph', 'content': "Because the access control is inconsistent, it undermines the confidentiality guarantees of the platform and could damage trust in the system's security."}] [1]

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Compliance Impact

I don't know

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Detection Guidance

[{'type': 'paragraph', 'content': 'This vulnerability can be detected by verifying access control behavior on the raw and direct file endpoints of the Flare application. Specifically, you should test whether authenticated users who are not owners or admins can access private files by using known or guessed file URLs.'}, {'type': 'paragraph', 'content': 'Verification steps include ensuring that unauthenticated users and authenticated non-owners are denied access, while owners and admins are allowed, matching the behavior of other endpoints such as download and thumbnail routes.'}, {'type': 'paragraph', 'content': 'While no specific commands are provided, you can perform HTTP requests to the raw and direct file URLs with different user credentials to check access permissions. For example, using curl:'}, {'type': 'list_item', 'content': 'Test access as an unauthenticated user: curl -I https://your-flare-instance/raw/file-url'}, {'type': 'list_item', 'content': 'Test access as an authenticated non-owner user: curl -I -H "Authorization: Bearer <non-owner-token>" https://your-flare-instance/raw/file-url'}, {'type': 'list_item', 'content': 'Test access as the owner or admin user: curl -I -H "Authorization: Bearer <owner-or-admin-token>" https://your-flare-instance/raw/file-url'}, {'type': 'paragraph', 'content': 'If authenticated non-owner users can access private files, the vulnerability exists.'}] [1]

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Mitigation Strategies

The immediate mitigation step is to upgrade the Flare application to version 1.7.2 or later, where this vulnerability has been patched.

The patch aligns the access control logic of the raw and direct file endpoints with the stricter checks used by other endpoints, ensuring that only file owners or admins can access private files.

If upgrading immediately is not possible, consider implementing temporary access control checks on the raw and direct endpoints to verify ownership or admin status before granting access, returning HTTP 403 or 404 responses otherwise.

Additionally, review and centralize access control logic in a shared utility to maintain consistency across all file access routes.

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