Executive Summary

This vulnerability affects Concrete CMS version 9.5.0 and below and is an Insecure Direct Object Reference (IDOR) issue in the AddMessage and UpdateMessage conversation controllers.

The problem arises because these controllers accept user-supplied file attachment IDs via the attachments[] parameter and load files directly without verifying if the user has permission to view those files.

Specifically, the system uses a function to find files by their ID but does not check per-file permissions with canViewFile(), allowing a user who can post in any conversation to reference any file in the CMS file manager by its sequential ID.

This effectively bypasses the file permission system, potentially exposing files that should be restricted.

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Impact Analysis

This vulnerability can allow a user with posting permissions in any conversation to access files they should not be authorized to view by referencing file IDs directly.

As a result, sensitive or private files stored in the CMS file manager could be exposed to unauthorized users, leading to potential data leakage.

However, the impact is somewhat mitigated if the site owner configures private storage locations outside of the webroot, which enforces permission checks on file views.

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Mitigation Strategies

To mitigate this vulnerability, site owners should set up a private storage location outside of the webroot. This ensures that permissions can be properly checked on file views, preventing unauthorized users from accessing private files even if they are linked or attached by authorized users.

Specifically, configuring private storage locations as described in the Concrete CMS documentation helps protect files from unauthorized access despite the IDOR vulnerability in the AddMessage/UpdateMessage controllers.

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Compliance Impact

The vulnerability in Concrete CMS allows unauthorized users to bypass file permission checks and access files they should not be able to view. This could potentially lead to unauthorized disclosure of sensitive or private information.

Such unauthorized access to files may impact compliance with data protection regulations like GDPR and HIPAA, which require strict controls over access to personal and sensitive data to protect privacy and confidentiality.

However, the Concrete CMS security team recommends configuring private storage locations outside the webroot to enforce proper permission checks, which can mitigate the risk of unauthorized file access.

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